Falty Receipts?

What is the name of your state? mi
Well here's something I need advice on - Went to court - sold a boat "AS IS" with a receipt stating boat sold "AS IS" - no problem.Buyer bought boat - blew engine 1 month after - tries to sue me for falty engine - said I new it was bad - when I did not and sue engine builder as well - case was falty misrepresentation.Anyhow we go to court judge figures I didnt build engine as I am a not qualified and engine builder states on stand he built engine and installed engine for me - so Im done right - wrong - well here it is - engine builder feels now he may be held liable so - engine builders business is incorporated.Both incorp and engine builder now bankrupt and closed for business - now they are saying receipts I have showing work done are fake - not real and have not real name of business on them as incorp was known as one name - his personal building business another? He said he did work that is on receipts but he never seen receipts before and title of business is different (slightly).
What the hell - how do I proove thats what he gave me - I paid him cash so no check's to proove - Im worried we'll go back to misrepresentation again -Please help I dont have a lawyer as its small claims and I didnt do anything to engine.

Oh yeah sorry - the case was for selling a bad engine which I know judge and lawyers know I did not - they are going after engine builder not really me - can I file something asking or requesting to release me because of lack of evidence or that they know I didnt do it and its hopeless for them to keep me going to court whilst they bark one mechanic versus another mechanic? Please tell me what I can do and do I send it to Courthouse or plaintif's lawyer.Thanx