Toyota Repair: 4-Runner tune up, 4runner sr5, headgaskets

Question
My 1990 4Runner SR5 has 184.5k miles, V6 3.0L engine, 4wd, and manual trans. According to the previous owner he had a tune up done, with hoses changed, can't remember about the spark plugs done last year in January. I feel that I should do another tune up simply because the weather where I live has been extremely hot (98+ degrees) all summer and the winter will bring freezing temps. Do I need to do a minor tuneup,or a major tuneup at this point? What are the parts that I need for each one?

I'm going to swap out the engine next year, when I replace the clutch, but I want it to run smoothly now. I have an oil leak from a rear seal and I've noticed that lately it has been running slightly rougher than before the leak started. Will a tune up help or do I need to hold off until that seal is repaired? Thanks in advance for your help.

T

Answer
I recommend that you find out why the engine has a rough running condition first, a simple tune up may not solve the problem, these engines had problems with headgaskets and valves, before I would put any money into it I would make sure the engine is mechanically sound, this means checking the engine compression and checking for a possible headgasket problem, there is a special service campaign(SSC VO-6)that addresses the headgasket problem, it may apply depending on the VIN# and if it has not been done before.