What could be wrong with this 2001 Grand Cherokee I just bought? 280,000 miles, 4.7L v8 engine...Any diagnostic insights?

First time buying a car, bought the Jeep Cherokee because I hear all the
time how reliable they are.  Bought it yesterday for a really good price (at
least I hope so, $850), but now I'm concerned about a couple things.

Here's what's concerning me about the car. (Everything I've noticed so far.)
-AC seems to blow cold but not strong
-Two back windows don't work, indicating possible electrical system
problem
-Dash board has a "check gauges" light on (wish it would specify which
one!! lol)
-Car needs a couple tries to turn on sometimes (seller told me he just
installed a new starter)
-Low oil levels
-Leakage under engine area of the car when car starts
-potent gas smell inside the car when turned on (that's how my sister
described it)
-Also, on my way home I drove over a high speed bump fast and I heard a
loud knock/thud sound in the rear of the car. Not sure what that was or if its
related to the other issues but thought I should mention. Never heard that
before.)

I checked the leak this morning. It starts when the car turns on. Its near the
front mid-left end of the hood, near the headlight. It seems the leak is
forming under a "hose"? I placed a paper towel under and the fuel is a light
brownish color and I cant detect what it smells like but I don't think its gas.
The leak also dripped small drops under several other areas but the puddle
was forming under one spot.

Ideas? Thanks!