Dealer rips me off twice

Took 4.5 hours to drive 40 miles back from lake on July 16th 2009. Took my $51,000 truck to dealer for repairs.This dealer has done all service on truck since I bought it there new. They charged me $839.95 when I picked it up on Friday July 17th 2009 and said it was the fuel pump monitor but it runs perfect now. Went home to hook up my boat to return it to my slip. Check engine light reappeared 5 minutes after I left my driveway. Had charters all weekend so I took the truck back for repair Tuesday July 21st 2009 8:00AM. They told me they would need it all day. Called me at 3:00PM Charged me $250.00 and said it was the wrong size air filter plugging things up. Total cost for repairs $1100.00. 100% their fault as they are th only ones who have serviced my truck since new. Told them I was not paying and they refused to release my truck until I did.