Am I being scammed?

I have 1977 Porsche 911. My mechanic has installed a new engine (said there was a problem with all original 1977 Porsche engines and need to be replaced). Something about rusted supports, lightweight engine needed. The problem I went in for was an oil leak and was told there were too many problems to fix and that's why I needed a new engine. The total cost for numerous repairs cost $27,000. Have I been taken?