Consider hiring a PI............................................

You have no damages to sue them for............

You can't. Courts don't get involved in this sort of thing.

I would hire a lawyer to review all the documents but, IMO, the burden is on you, not them, to determine if the upgrade is compatible with your car.

Same way you find a mechanic to work on your car for cheap. Call a bunch and ask them.

This is not a legal issue. Start with the vendor.

This general Q&A forum is not a substitute for specific advice on a specific case. You need counsel. Our opinion as to what the judge did is...

You can sue anyone but IMO, your suit will go nowhere.

IMO no. Your address is public record. ......................

You can't. They both have immunity...................