Welcome to the Two-Week Club! My initiation was courtesy of Four Seasons. Just finished replacing my housing for the third time. Went with the Motorcraft housing upgrade once again and this time used a Motorcraft t-stat. Properly torqued everything...so, we'll see how it all performs this go-around. If there is a next time, I'll be looking at the metal housing, too.
I have never had an issue with plastic breaking off on my own vehicle during these installations; nor, when I've removed many manifolds off trucks at the JY. If you haven't already, replace the lower manifold gaskets and PCV valve. Other than that, the short water hose between the t-stat housing and water pump. Suppose you could get really involved and clean/replace fuel injectors.