It would help to list the full specifications of your truck including the engine (4.0Lv6/4.6Lv8), transmission, 2WD/4WD/AWD, etc. Some of what you will need to do depends on these options.
I would develop a plan to carefully examine your truck and put together a list of parts. Make one list of parts that need to be replaced now and a second list of parts that can be replaced over time.
Do an examination of the suspension including the bearings, struts, ball joints, tie rod ends, and bushings. Learn how to check each component to recognize when it is gone or going. For suspension parts, try to stick to Moog Problem Solver, SKF, KYB (for struts), or Motorcraft. Motorcraft will almost always be the most expensive and not necessarily better. If those parts are too expensive, ask here about specific parts from other brands that users have found to give good service.
You could replace any of the things you mentioned on the engine but most of them I would leave until they show signs of problems. Depending on the engine you have, the most important thing to check and maintain could be the timing chain setup. Carefully look over the engine for signs of leaking fluids including the oil filter adapter, valve covers, oil pans, and timing chain cover. Check for leaking coolant around the thermostat housing, intake manifold, radiator hose connections, and heater core connection.
Check the drive train for cracks or splits in the CV axle boots and signs that the differentials are leaking where the CV axles insert.
Check the brake lines for any signs of rust or leaking brake fluid. Look especially around the flex hoses at the wheels and the flex connections where the hard lines come off of the ABS pump.
Check the power steering system for leaks or excessive rust on the metal sections of the pressure hoses. Make sure that the dust boots on the ends of the rack and pinion are not cracked or torn and don't have any PS fluid inside.
As stated by others, the best preventative maintained you can do now is to replace fluids, including the transmission fluid and filter.
It is more important to ***** your truck and find parts that need replacing then to just start replacing things by guessing. You could end up spending allot on parts that are fine and miss things that need fixing.
If you plan on keeping this truck for the long term there is no harm in buying parts that you may need to replace in the future if you can find a good price. Some parts for these trucks are getting harder to find and are not likely to get less expensive over time.
LMHmedchem