Engine swap ease is relative. It can be a pain due to rusted out bolts, parts, etc. Sometimes there are subtle changes you'll run into as well.. There are little tricks to stuff sometimes, like for example seating a torque converter in an automatic trans. A lot of people seem to have a lot of problems getting to the bell housing bolts, just stuff like that.
Check your oil for coolant.. As for "it wouldn't start", was the starter able to turn the engine over? Can you turn the engine over by hand with a 1/2 breaker bar or socket wrench?
Pete
Edit:
If you do put the new(?) '86 engine into the '90 listed in your profile; this is a good example of it not necessarily being a direct drop in. The '86 has EGR and the '90 doesn't. You'll want to swap the upper intake plenums (sensors and all) and use the '90 exhaust manifolds.