I picked up an Abu Garcia 5600 C4 last season for $94. I also snagged an old 5000 on Ebay for about $30. all that one needed was a clean and lube and its good for another 30 years.
I have actually used the I boats site to find the part # and taken that down to Napa and had them order the parts. as long as you can find the part # more than likley your local parts store can get it.
have you checked the hub on the prop? I have heard of the rubber going bad and the prop spinning on the hub.
does it shift in and out of gear smoothly?
the engine is not going to blow. its just going to bounce off the rev limiter. no harm can be done. go out in your car right now and hold the gas pedal down in neutral. it wont go past about 4500RPM's