Really have to know what broke to assign blame. If a keeper came loose and it dropped a valve its the machinist's fault. If it broke a valve stem off cuz you were too cheap to buy new valves, well... If you can't do the work yourself, then you're gonna have to pay somebody to fix it. Just make sure its the right somebody.
From what I've seen, if there is a problem when it was put together, the engine will fly apart in under 300 miles. Remember my 235 that flew to pieces in 120 miles? Lets just call that one a "supplier issue". But know that I feel your pain. :o
best of luck
chip
