Sorry if I appeared thoughtless. You'd need "knowledgable help," certainly, to do the deed in a weekend. It took me a terribly long time simply to swap an engine and A/T combination recently. Oh, yeah, it's not done yet. After four weekends. Gee, I guess I can't estimate very well. But in the best of worlds, what you're considering is a weekend operation plus the head preparation time.
Your car was tempting for me when it was on Thackeray's web site. On all but one of the 164's I've bought, I've tended to the t-belt immediately. That sole exception is a car that came from the DiMatteo family in Florida -- used to be Fred DiMatteo's car. It appeared to be in good operating order, although it had been out of their hands for a few months when I bought it from an Ebay used car dealer. Even on that one, the tensioner went "sproing" and the outer spring broke as I dismounted the tensioner to replace the t-belt six months after I purchased the car. Coulda happened earlier, and I'da been outa luck.
One car came with a mis-installed tensioner and a floppy belt. I'm just lucky not to have had my lunch eaten by that one. Another came with an already broken outer spring (the one which jumped time on the P.O. and he spun a bearing). Two others came with intact tensioners, but we didn't even start the engines before exchanging belt and tensioner. I've not yet had the misfortune of losing a tensioner in service, and I like it that way. But that mis-installed one was a near thing. Half of my personal automotive mechanical experience has come working on our 164 fleet after january 2004, and I fully understand not being confident on things I've not yet touched personally.
Michael