If I was you I would start planning on going threw everything listed above if you want your ride to last. Used car owners tend to forget how many years of wear and tear the parts on their cars/trucks have taken. From my experience when things start falling apart on older vehicles it's like an avalanche of things falling apart. Think about it. If a part made of rubber or plastic falls apart there is a great chance all of the other rubber and plastic parts similar to the one that fell apart will be failing soon. Basically if you plan on being a used car/truck owner and don't want to find yourself in the typical, "$hit now I can't get to work" situation because your ride broke down, You'll need to stay on top of replacing everything at some point. I'd start with the parts that could cause a very unsafe situation i.e. brakes, steering, and suspension. Then go strait for the timing belt, cam/crank seals, water pump, belts, and hoses. Next I'd tackle the vacuum lines and hoses. Then lastly I'd go after the fuel filter, trans cooler (bypass the radiator and buy a nice large external cooler), ignition system, and replace or find replacements for all of the ECU connected sensors. You don't need to replace them if they aren't bad but finding an keeping a replacement will prove to be a huge stress saver when one of them does fail on you.
If you do all of those things your ride will last you many many years to come so long as your engine and trans are up to the task wear wise.
To many people buy used cars for 1000 or 2 and expect them to last forever just because they ran good when they got it. The above might sound like a ton of money but think of it this way. A payment on a new car would get you for an extra $200 - $600/month for a reasonably priced ride. Then tack on the full coverage insurance and any maintenance costs along the way. If you took half that money every month and spent it on your used car you'd have a really nice ride in a very short period of time. The new car will start to look like $hit and start falling apart in that same period of time after spending twice the money on it.