If it goes to court the judge, in all likelihood, won't care about USPAP issues or even the other errors. His concern is "is the appraised value credible", not how he got there.
If the value is reasonable, tell your client about the errors in the report but that you agree/mostly agree with the final number. Let the lawyer take it from there. OTOH, if they want you to do a full review and are willing to pay you I see no reason not to do it. I've done it several times. When you get down to it, the legal system for civil courts is all a big game and lawyers love running up billable hours and spending their client's money.
Review it in a professional, objective manner and let the lawyer skewer the other appraiser on the stand. When the case is concluded, turn the other report into the state.