I will apologize in advance because I know the answer is probably here on this site, but I'm having to make a decision quickly and just need some advice/answers/opinions quickly. So in advance, thanks for any help.

Here's the deal. I want to buy a 1992 240GL automatic from a co-worker. He is the third owner of this car and it sounds like it has been upkept well. There are some minor things wrong with it: the check engine light comes on, the back brakes don't light up and he said fixing it requires taking the back panel off (what would this cost to fix?) and he said there was an oil leak that after a good bit of time trying to fix, his mechanic finally got fixed. The car has 135,000 miles on it and is in good shape interior and exterior.

Honestly, I only need this car to last me a year until I get out of school, but I drive 45 miles round trip each day. It's not diesel. He's asking $2400 U.S. for the car. I'm not mechanically inclined, so if anything breaks down, it's to the repair shop it would go.

Here are my questions:
What kind of gas mileage could I expect?
Will it hold up for that kind of extended interstate driving?
I've read on here and other places and I know Volvos last forever, but is this a wise investment.
I've also heard parts/service on Volvos are expensive and I'm not rolling in cash. What could I expect?
What could I expect in terms of future upkeep/maintenance costs?
Last, would your basic auto mechanic be able to at least look at it and make sure the engine is sound?

Again, thanks for the help and apologies because I know I'm asking stuff that's already been asked, but I'm desperate. I have to make a decision tomorrow.