If any camshaft related part broke at 5000 miles and went loose into the engine bottom, the timing chain tensionner is the prime suspect. Loose parts are quite unlikely at such low mileage, unless someone did unscrew and dropped in or broke the timing chain tensionner bolt for instance. If so, this missing part is visible. Recovering the broken piece requires to split the crankcase and it may already have caused extensive damages, because adjusting the tensionner is done with the engine running. It will at least cost you about 15-20 hours of labour, a new tensionner and new gasket set. You are better to look for a replacement CM400 or CM450 engine.