Get a reputable/trustworthy mechanic to run through the car, if they pick up the same faults, do research and purchase the parts yourself on the cheap.

Then get said mechanic quote for labour on replacing the parts

Indication of prices you should be paying:
RTA bushes $60, labour $150
2nd hand OEM shocks ~$50. New KYB shocks (OEM replacements) $200-250. Labour no more than $100
Rear muffler, get a stock one for $20 and weld it on for another $20
Distributor o-ring is like $5 for a pack of 1000000... labour to replace and readjust timing should be no more than $50
Rocker cover gasket, DIY it
New OEM replacement rotors and pads should cost you no more than about $400 installed. Cheaper if you buy it yourself obv

These are lower end prices, but should be what you're aiming for. Don't pay a fortune on a 14 year old civic, be smart