The VIN number and vehicle description do not match and I think the car dealer hid problems. Please help me figure out what this all means.?

A couple of weeks ago I purchased a 2004 Ford F350 Lariat. Before I purchased it the dealer said he had it at the mechanic to fix a leak that they couldn't figure out. He promised it would be fixed. They are a family dealership, and although weary, I did trust them.

The dealer showed me a Carfax with a high score (which means little to me), and I asked him in front of my son, "will the leak problem be solved?" He said "Yes", I said, so if I purchase today and I get home and there's a problem what happens? He said "Then bring it back."

The leaks continued, and now there are diesel fumes in the cab when I turn on the heater. I planned to go down Monday to make him fix it as promised, but then I started to get suspicious. So I ran an autocheck.com report. The report says a few interesting things. First, the VIN # lists an F350 Harley Davidson King Ranch" truck. Ours is just a Lariat. It also says the title was "corrected" 3 times, and that was a few days before it was reported at the DESERT SOUTHWEST REGION auto auction and a week later reported as "Registered at auto auction as dealer vehicle." He said 2 owners and NEVER told me about the auto auction. Another thing strange is that he sent us the dealer plates but no registration.

I need to go settle this Monday, and I think he pulled the common auto dealer lying by ommission tactics. so my questions mainly are why a title would be corrected 3 times, and if the VIN is wrong...the VIN is wrong...right?