score:9
The travel desk at my hotel has made some calls so I'll share the information.
Actually there was a misunderstanding about when I should pay so my hotel actually took my passport one day later, when I had only two days left on my visa! And I did get it back the same afternoon. And it did cost only USD $40.
I haven't checked any other hotels or travel agents but my hotel was Hotel Tulip Xanh, which has a travel agent on the ground floor. So if you have trouble finding the same or lower place anywhere, this is a place to come. Their address is: 80 Hải Thượng, tp. Đà Lạt.
Upvote:2
I don't think there is a legal XX number of days in advance that you are restricted to. It is more the legality of being in the country without proper documentation.
Agencies advertise rush three day service, so less than a week is possible. But you don't want your current visa to expire before a new visa is issued. As one must assume a day to get the paperwork to the Immigration folks, a day for processing and then a day to courier it back, you best get your ... in gear.