Since the engine won't start, I would take it apart and find out what the problem is. You may find something broken that is easy to replace and not too expensive. 70,000 miles on a properly rebuilt engine is nothing (the engine is just really getting well worn-in since it should go 500,000 miles) and the failure could be a defective part that did not damage anything else or very little damage was done. That is, if you can do the labor. If not, then factor that in to your decision to rebuild or replace with a used or rebuilt engine. If you spend some time a used engine can be found at a reasonable price in good condition (perhaps a rusted-out body with a good drive train). eBay is a very serious caveat emptor place to buy from and eBay does not protect buyers very well. Junk yards are one place as well as ads in papers and Auto Trader.

My $0.02 Worth!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.