How much you guys think it'll cost me to get an amp and a bazooka tube installed in my car ?

ill do it for 50 :)

lol i wish i was in texas

Depends
roughly 120 though to be done professionally, i'd say with a leeway of 40 bucks both ways
plus extra for products like wiring

Do it yourself. It's really easy
go to circuitcity.com and i believe they even have a general DIY for amp and subwoofer installation.
It will save you a little bit of money