Well, the bad news is, it's going to be hard to go from don't-know-a-thing to amateur-mechanic in a few intarweb posts.
The good news is, buying an $800 car, a $50 repair manual or two (the factory service manual is the ultimate reference; for the Tracker's, I'd say the Chilton is the better at step-by-step guides. Ideally, buy both and a Haynes
), and $200 in tools, and leaving something in the budget for eventual parts, is a very good way to gain experience in a hurry
All the manuals are a bit of a choose-your-own adventure, with the downside of not telling you which pages to go to next... The factory service manual, for instance, will give you the order in which things need to be dealt with, but is a bit sparse on details of what to *do* at each step. Chilton at least makes complete sentences, rather than a mere list of engine parts, but you still have to devine that there's a page *somewhere* in the book that gives details on how to do each step. But they don't bother cross-referencing, and the index isn't always a help in finding them...
For your check tomorrow:
The oil dipstick is at the front right (right when facing forwards and driving the car; it'll be on your left if you're standing in front of the car looking in...) of the engine. The oil can be a bit brown and dirty, but shouldn't be white and frothy. White and frothy means radiator fluid in your oil, suggesting a broken head gasket, which requires tearing the engine halfway down. Instructive, but a lot of work
There'll be another dipstick somewhere for the transmission fluid. The stuff on the end of that stick should be pink, apparently. Dirty transmission oil is a bad thing, but I don't like auto trannies, so I duuno *how* bad. The radiator is at the very front of the car; on the left side of that there's a small white plastic bottle. Make sure the stuff in that is clear and (usually) green (could be another colour, though). Brown and sludgy is bad. That would mean oil in your radiator fluid, suggesting a broken head gasket, which see above.
Not sure about the top. Obviously, just looking at it for holes. I suppose you could spray it with a garden hose...
One thing to try check is to peel back a corner of the carpet somewhere and see if the underlay is all wet. If it is, there's probably rust holes through the body (or a leaky top might lead to the same). Seriously problematic places to have rust would be where the suspension mounts bolt to the body. You can see the front ones on either side of the engine bay. It'll be obvious. Another problematic place to have rust is on all the bolts in the engine, which you'll eventually end up swearing at when you need to remove them to replace parts, and they don't feel like being removed. That's harder to check, though.
Agreed that a compression test is probably the most informative thing you could do. To do that, you need to make sure the engine won't start (to be honest, I got lazy and skipped this step when buying mine, so I'm not sure if you do that by grounding the wire from the coil to the distributor, or by clamping off a fuel line, or by disconnecting the fuel pump, or some other way.) Then, you remove the spark plugs. Then, you take a special compression tester, thread it into each spark plug hole in turn, and crank the starter motor a specified number of times. If the engine's healthy, the pistons generate good compression. If the rings leak, or the valves leak, or the timing belt has slipped, then they don't. Any of those problems require a full tear-down of the engine. Which is instructive, but a fair bit of work
All that said, first on my list of things to avoid would be automatic transmissions. But you know what they say about opinions: everyone's got one and most of them stink
