score:6
The phone should still work as long as it didn't die in the meantime - but you can try that out at home.
The question is more whether the sim card still works. I assume it won't. In most countries sim cards expire if you don't use them. Sometimes after 3 months, sometimes after 3 years, so after 7 years it very likely did. So even if the phone still works, you will probably need a new sim card.
However, you should not need to buy a new phone. Just use your regular phone while you are there. Power is not an issue. You can buy a local charger on very little money.
As for the plan, you have two options: