Mate - those monkeys obviously don't know how to do even the most simple of tasks. Stay away from them, try visiting your nearest club instead.
Removing a flywheel = box spanner, mole grips - or decent adjustable pliers. A careful tap or a little leverage will see that the flywheel comes away from the conical spacer on the crank. Just be careful with the front bearings rubber seal - don't damage it. There's NEVER any need to mess with jamming the piston when removing the flywheel. Unbelieveable. Those idiots owe you a new engine.
1) Remove cylinder head - usually a simple case of removing hexhead bolts or screws.
2) Remove the glow plug button and shims.
3) Remove backplate - some competition engines require you to have the piston in a certain position so that you don't catch the piston on the back plate. Most cheaper engines don't.
4) Remove the manifold
5) Put the piston to BDC (to the bottom dead centre)
6) Insert a thick Nylon tie wrap through the exhaust port.
7) Turn the crank, 9 times out of 10 the piston will drag the sleeve up with it, thereafter enough will present itself for you to be able to pull the sleeve out.
8) Note the orientation of the sleeve, but usually there's a locating pin so that you cant fit it the wrong way.
9) With the sleeve removed, you can easily pop the conrod off the cranks big end, and carefully pull it up through the top of the engine.
I hope this helps - and I'm sorry to hear you've been let down badly by your LHS. Please bear in mind that, fortunately, not all LHS are that stupid.
[Edit - to correct sentence]