I'm running a .50 raptor

I think i've overheated my engine 1 too many times. Now it wont start. A freind at the hobby shop thinks the engine has no more compression. If that is true, should i change the piston and piston ring? Maybe even change the piston liner? Would those 3 items give me back the compression I need? Am I even in the right ball park?

Or is it unrecoverable? Should I just go out and buy another 50 sized engine?

Thanks.