How about.. Don't go near that LHS again! Crushing a piston? man. I've never had to touch the bloody piston (or any internals) to remove/add a flywheel..

Mate, all the info you need is on your computer so sit on ur ass and do some reading Piston and sleeve replacement is pretty easy, im sure there are instructions around if you search (google and this forum).
The "good deal" is a good deal for them as u return to buy spares for the sirio, sounds like they broke a perfectly good engine then sold you a worn out one!

Actually I would go back to the LHS, just the once to return the sirio and get ur $$ back.