4age in my books would be in in the meduim range as a engine conversion a lot of little things need to be modded and fitted.
I think the best starting point for anyone to learn how engine's work and how to put them back together is a good little K . Buy a K enigne for $50,slowly strip it and look at how everything moves and works, change bearings, gaskets , timing cheains , rings..then put it back together.
Best $50 bux you could of spent.