The factory exhaust was side exit. Sounds like someone has an aftermarket muffler on it if you can hear the exhaust from inside. Either that, or they just have a cat on it and nothing else. A good, quality paint job? How much did you pay for the truck? You may be looking at investing 50-75% of that cost in a really nice paint job. That truck has a LOT of area to cover, and the labor is what's gonna kill you. Like Kodiak said, unless there are a lot of flaws in the paint, hold off on it for now. A lot of people will have different opinions on exhaust brands. Flowmaster, Dynomax, Delta-flow, etc, are the common names. I wouldn't recommend glass packs, though. Go with a turbo muffler like Flowmaster or Dynomax, and get the exhaust straight out the back, with dual chrome tips. The longer the tips, the deeper and more mellow it will sound. I would recommend a single in-dual out muffler, unless you are getting headers and plan on running true duals. Then dual single in-single out mufflers will work.
Randall