Hi Heavrolet!
There isn't much to tune-ups for these old girls... unless you need to do some serious maintenance.
Basic stuff, go ahead and change the fuel filter (I use Wix).. make sure you keep the GM ring and housing if the filter you buy has the all-in-one cap. (you might need the original one at some point)
You're done.
Just kidding...
Print out the checklist in my signature and use it as a guide... it tells you about most of the stuff you need to do. Fill it out as you go, ask about things as you go along, we'll help you out.
Stuff you want to make sure of, this time of year:
-- check your coolant level and concentration (on, I see you're not int he real world... not as big a deal down there)
-- clean all battery terminals - you should do the battery post mod
-- check your serpentine belt - small, lateral cracks on the inside are ok as long as they don't go right through, any longitudinal cracks mean you need to change it, check the tensioner to see if it is between the marks
-- clean grounds!! pay special attention to the strap at the back of the engine, passenger side
-- check your air filter, blow it out with air
-- pull your fuses, one at a time, clean the spades and clips, put 'em back. NalOx works great for this
-- ohm out your glow plugs and clean the spades
-- check your starter bolts to make sure they're tight... make sure you have the front bracket on the starter that holds it tight to the block
-- clean your radiator through and through (external) - use some foaming cleaner and a garden hose (not a pressure washer). Wash from back to front, take your time and let it soak. If you have overheating issues, we'll walk you through how to REALLY clean it.
That's all I can think of, off the top of my head. Once you have the whole checklist filled out, come back and post your findings here in this thread (copy/paste a checklist in a new post, then fill in the blanks with a different colour) and we'll all be able to 'see and hear' what you've done. More ideas by then, I'm sure.
Welcome to 6.5 country!