Tune up a 95 4cyl

taking in my 95 tacoma 4 cyl 2WD manual 213K miles for a tune up tomorrow. After checking this site out I think I should have just done it myself however.....I'm a read the directions and then DIY'r and have to be pretty sure of myself first. Haven't done a "tune up" yet, just changed plugs, oil, filters, etc. so..... I'm told the tune up includes plugs, wires, air filter, cap and rotor and a fuel filter. I asked about the timing and they kinda just looked at me...if ya haven't guessed..I am a woman..and yes blonde but hold off on your judgment just yet!! I've checked it out and it seems I have a "chain" not a belt. I know this hasn't been changed etc. for at least the last 120K miles (this was my kids truck....). Now given this info, should the timing chain be part of this tune up at this point? When doing a "maintenance tune up" as they put it...should they be checking the timing etc? If there is really nothing to check so be it....I should have done the work myself. Anyhow, they are dinging me for 400 bucks and it looks to me the parts come in under 200 so..... While I got ya, the air conditioning is shot on this ole girl and the belt was wailing so, per the shop, it wasn't needed and they simply cut it off. Anybody know of any problems running without this belt? Also, saw some threads about having the "throtle" checked/cleaned...can I get some info on what, where it is etc? Truck lost it's oomph and gas mileage is down....