there have been incidences of the cam chain tensioners being incorrectly installed (several threads on the ratnet) with bad things happening shortly after.
the tensioner is a ratcheting mechanism and if not re-set properly, then its all bad. If they are saying the crank gear is damaged, then I would insist on a new cam chain as well as it can not have been unscathed by this. I would also want a good look at the chain guides for damage as well.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter