Has anyone had the exhaust mixing elbo and associated gaskets, hoses, etc. replaced professionally? The yard I am working with explained that the teak cabinet in the aft cabin would need to be removed. It appears that all is accessible by removing the engine cover and aft access panels. They estimate 10 hours labor for the entire job, a $335 "machine shop welding fee", and approximately $200 in parts. Does this appear reasonable? The boat is a 1988.