White smoke, very bad fuel loss, stalls when trying to idle

Jeep cherokee. Ran with no white smoke and was good on gas usage, though you could feel slight hesitant on gear shifts..
What happened is one day it didnt want to start, acted as if the battery died over night. I tried to jump start it. Found out he battery is fine, but it will not turn over as if not recieving gas. Took it in to get fixed.. A day later with a 340.00 bill, the truck starts now but with these symptoms that were not there prior before taking it in (white smoke, burns gas like hell, stalls when idle have to keep foot on the gas peddle, and now two missfire spark plugs perhaps)