With 6 years & 60,000 miles since the last maintenance (other than oil & filter) you're probably right that it's time for a bit of TLC.
Timing belt can be a bit tricky to install right (needs special tools), but it's probably time for one especially since you don't know if it's been done....
Many posters here decide to do a LOT of "preventive maintenance" at the same time as doing the belt, to avoid digging into the same area again when something else needs attention. Water pump being the main item (even if OK now) with serpentine and it's tensioner & idler pulley next on the list since it has to come off to do the timing belt.
Tune-up wise, there really isn't a "tune-up" list anymore per se - spark plugs being the only "traditional" tune up item left....
A major tune-up at this point for your car (IMHO) would start with pulling the plugs for replacement (checking condition & deposits on the old ones for diagnostic info.) then doing a compression check to get baseline #'s and check engine mechanical condition before installing the new ones.
Next would be inspection/replacement of of common items that may be worn out at that age, starting with PCV hose & valve (collapsed/holed not uncommon & a "rough idle" possible cause) followed by plug wires (lifetime warranty ones often recommended here).
While you're messing in the area, it's a good time to remove the coil pack & check the base for cracking, as well as checking it's connector "pigtail" wiring (two areas we've seen that can cause running issues)
A general inspection would also be in order, the things to look at would include checking/cleaning battery terminal connections - wiring ground connections - vacuum hose condition - all other fluids/hoses etc..
It sounds like a lot of work, but the main idea here is just to take a look around & see if things look OK or if there are any obvious problems in evidence.
Just changing the plugs & checking the PCV might be enough to solve your rough idle issue, in any case this kind of "basic" maintenance needs to be done before looking deeper for an issue because otherwise you could be looking for a problem that doesn't exist!
Good Luck & get back to us with more questions as needed...