Wow, I've had that work quoted at around $400 to $500.  Where is that local CAT Dealer?  Was the issue the "access".  I know that mine, with no rear slide is easier to access.  Like you I have not been able to determine that a record existed that the work had been done, but I got mine at 65000 miles and I would therefore assume that someone, though not necessarily a CAT dealer, did the work.  Although I may be wrong, the engine has performed fabulously including both Jakes, and I am just very leery of having it opened up at this point.  I may change my mind but wow $1200 just to adjust some clearances seems way too high!
Mike