Does everything happen for a reason?

Yes. Everything happens because of a reason, a cause. Otherwise there can be no enlightenment.

People normaly act "for a reason" but to put it right, phenomenas arise "out of reason", have causes. So by focus just on giving right causes, phenomenas appear likewise, are experianced according the causes given. The highest cause to go beyound being subject to causes, is the fullfilment of the Eightfold path. There is just one unconditioned Dhamma, yet not to be found without giving the right causes.

All beyond that, beyond the all, is just philosophy.

'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range."

One saying: "Not everything happens for (better 'out of') a reason." would not speak in accordiance with the Dhamma, does not flow in the stream of Dhamma. Since: By touch dhammas are experianced. Every explaining else is not really possible and subject to errors. Suttas have to be readed carefully, with proper attention, seeking release not something to grasp. Otherwise the Dhamma is like a snake grasp on its tail.

[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]

In general, of course, unlikely events are accidental. And physical events, such as an earthquake, are always accidental. But, if an event, such as meeting someone seemingly by accident, is caused by somebody making decisions, it is remotely possible that karma may be involved. Old friends for previous lifetimes sometimes seek one another out by unconsciously making the right decisions that lead to an “accidental” meeting. Such events are rare. And, when they do occur, there is usually supporting evidence, such as finding one another very familiar in the case of a meeting of old friends. I would suggest that you look for substantial evidence before “embracing” such an event, especially if it requires significant cost or sacrifice.

In the Sivaka Sutta (SN36.21), the Buddha explains that not all experiences are caused by kamma. Sometimes, it's just the weather or something else that's not extraordinarily significant. Not everything happens for a reason.

As he was sitting there, he said to the Blessed One, "Master Gotama, there are some brahmans & contemplatives who are of this doctrine, this view: Whatever an individual feels — pleasure, pain, neither-pleasure-nor-pain — is entirely caused by what was done before. Now what does Master Gotama say to that?"

[The Buddha:] "There are cases where some feelings arise based on bile. You yourself should know how some feelings arise based on bile. Even the world is agreed on how some feelings arise based on bile. So any brahmans & contemplatives who are of the doctrine & view that whatever an individual feels — pleasure, pain, neither-pleasure-nor-pain — is entirely caused by what was done before — slip past what they themselves know, slip past what is agreed on by the world. Therefore I say that those brahmans & contemplatives are wrong."

"There are cases where some feelings arise based on phlegm... based on internal winds... based on a combination of bodily humors... from the change of the seasons... from uneven care of the body... from harsh treatment... from the result of kamma. You yourself should know how some feelings arise from the result of kamma. Even the world is agreed on how some feelings arise from the result of kamma. So any brahmans & contemplatives who are of the doctrine & view that whatever an individual feels — pleasure, pain, neither pleasure-nor-pain — is entirely caused by what was done before — slip past what they themselves know, slip past what is agreed on by the world. Therefore I say that those brahmans & contemplatives are wrong."

If something unexpected (and incredibly unlikely) happens, should we take it as something deeper or just a fact of life?

Something highly unlikely and very positive happened at a very bad and negative point in my life, this event arguably showed a very different future to the one I imagined.

The Buddha taught that there are 5 natural laws (Niyamas), that causes physical and mental events to take place;

1. The seasonal laws (Utu-Niyama) related to temperature, seasons and other physical events

2. The biological laws (Bija-Niyama) related to seeds and physical organic order

3. The physical law (Citta-Niyama) related to the processes of consciousness, or to the nature of consciousness which recognises objects etc.

4. The Kammic law (Kamma-Niyama) related to the law of Kamma, (good deeds and bad deeds and their results)

5. The Natural laws (Dhamma-Niyama) related to certain events: the general law of cause and effect, causality conditionally and unconditionally Trying to further interpretate it will just carry over into imagination. Only a fully enlightened Buddha can know the intricate workings of kamma.

Don't know how to read into it, or how my actions should be after the event, should I embrace the change?

You could treat it as you would do in Vipassana meditation, i.e. to treat all physical and mental objects the same way.

You can also use it to further deepen your practice. If you have increased time and energy, you could practice Dana and do e.g. volunteer work. Its really up to you.

The Buddha taught that one should do good, practice the Dhamma and lead a pure life.

Nothing happens for a reason. Reason is something given by us. Everything except Nibbana happens & happens due to causes. Nibbana doesn't happen, it is existent. Thus not caused.