This is timely!
We are selling our above ground pool and getting a hot tub this Fall, as well.
Some of the considerations have been the electrical box, running the electrical underground a few feet so no one trips on it (in our particular situation, yours may be different), having a concrete pad poured, having to take out part of our fence to get it delivered, deciding which way the wind blows in the winter so we know which way to face the holder for the lid so it breaks the wind, what kind of lid holder to get, what kind of lid to get, decking and where to get the tub itself...the list goes on.
We found the least expensive place was Home Depot (We live in Canada, in the US may be different), as the actual spa places prices were crazy however, if you need the whole package with installation then you may have to go that way. My husband is going to do most of it himself.
There is a really cool lid that raises up hydraulically to create a roof and then lowers to create a sealed cover but it is dreadfully expensive. We will likely just get one of the lids that are insulated and fold back into a holder behind the tub during use.
I plan to use it in the Summer just to float in...the one we are looking at is big enough for one person to do that.
I'll ask my husband about your question re: leaving it while you go on vacation.
Watson