Does he have a printed estimate that states what part he was supposed to get? Emails? Anything that is physical evidence that can be printed out and handed to a judge. Documentation, etc.
If it's just 'I told him X and he installed Y' an attorney isn't going to be able to help.
For example, if you asked for a Rock Krawler X factor and he installed a stock mod: If the estimate just says: "Rock Krawler lift kit", you're done.
That is exactly the problem I think I will run into. The parts list I have isn't very detailed, the part in question on the list shows as "Dana 60 with larger brakes". Now to a Jeep person, or even more so a JK person when a Dana 60 is put into a JK there are two different ways to do it. 1. A Dana 60 with 1 ton knuckles that requires a larger brake setup. and 2. A Dana 60 that can use the stock JK brakes with no modifications.
So when I saw my parts list and right on the top of the list it says, Dana 60 with larger brakes--------7100.00 , I knew without a second thought I was getting a 1ton front Dana 60.
Now when I picked my Jeep up, of course I took it for a test spin, looked it up and down said to myself, yup sexy Dana 60 front and rear axle's, really cool lookin EVO Double throwdown front and rear, damn I am set to go give this thing a offroad shakedown.
So several days later I did just that. After about 4 hours of mid-to-mild Iowa dirt wheeling (Less than 10 miles total) I broke a passenger side axle u-joint and tore up the stub shaft. Pulled the shaft out, and drove it home. Shot an e-mail to manufacturer and asked to get a replacement stub-shaft and a u-joint. They replied they needed the original order number to look up the axle to make sure they got me the right parts. So I got that from the installer, and forwarded it to the manufacturer, got reply back in minutes " That's just a standard OEM sized JKD44 stub shaft that is Chromoly, would you like me to send you one it's $$$.... At this point I ran out to the garage grabbed both the stub shaft and the inner shaft and looked more closely.... AND OMG he was right they were roughly the same diameter of a D44 shaft. (Sweaty and dirty on the trail I had not noticed this when I pulled them out). Long story short, I got a Dana 60 housing with Dana 44 knuckles and Dana 44 30/32 spline shafts, which when put on a 500HP Hemi JK running 42" tires is just freakin stupid... I paid for and was under the impression that I should have had a true Dana 60 with 1 ton knuckles that required the "Larger brakes" portion on the parts list.
So talking to the manufacturer the axle I got costs roughly 5500.00, the axle I paid for and didn't get is 7125.00
Due to the lack of detail's on any parts list, I most likely have little chance of getting this resolved shy of the installer stepping up to the plate and making this right.