Diagnostic services service near Sterling, VA

These days it's hard to find a Mechanic/car repair shop that one can trust to do professional work and customer service. In June 2015 I bought my 2000 GMC SUV Jimmy to Mark Auto Service of Seat Pleasant, MD PROBLEM: engine misfire. hard to start in the morning. Told I needed a fuel pump COST: $500. Two days later, returned with same problem. 'Said' Zaatra (shop owner) now tell me I need to replace the fuel Injector. COST: $540. Return back in 2 days at the shop. Problem not fix. It's has cost me $1040.00 for two misdiagnosed's. I took it another auto repair facility...they were able to discover the problem and FIX IT. Turn out all I needed was a 'TUNE UP' (Spark plugs) MARK AUTO SERVICE refused to refund. As a CONSUMER...I cannot allow this shop owner Mark Auto Service get away without taking Legal Action.