timing belt should be changed together with a water pump and cam/crank seals, tensioner, idler and thermostat like every 90k miles.
sample of a nice (OEM) timing kit (it includes all that's needed even new drive belts):
http://cgi.ebay.com/ebaymotors/Fits-...Q5fAccessories
$169+s/h
rest is labor, which at the shop takes a lot of money as job takes time (4-6 hours depending on what items are done).
you can get the tune up done on it easily (if that is 4 cylinder we are talking about), get new NGK Iridium-IX plugs, new NGK wires (amazon cheapest or Advance Auto locally), new fuel filter from dealer, new air filter (any, even FRAM will do), new PCV valve+grommet from dealer. might also clean the Throttle Body with Sea FOam deep creep or something similar and oxygen sensor safe.
might be a good idea to start flushing all fluids if they were never changed.
question is is you want to that all on your own (cheapest method) as investing tons of money at the local shop on something that is not worth much and/or was neglected and might fall apart soon is not the best idea.
vibrations in reverse might be a few things, but most likely the engine mounts are worn, replacing all of them is pricey (top, front, rear and transmission, all OEM are like $280 for parts only at online dealer) especially when done with OEM parts and at a shop. check the exhaust flex pipe for cracks, usually it's burst open when mounts are worn out badly.