It's not that hard, as long as you can do some homework, and get things lined up ahead of time (collect all the parts needed, check your list twice type of thing) And or if you know a reasonably good shop, or some friends that can help etc...
I was lucky, I had a mechanic/welder jack of all trades father growing up, and I always paid close attention to what he was doing. So by the age of 3, I was taking my bike apart and putting it back together... and just never stopped working on things since.
Obviously, you would want to get the car as far on the low end as possible. And if all it needs is the motor, you'll be able to find one in no time. Have some of the local guy's help in that search too.
It all depends on what you really want, and what you can afford time wise. If you have the tools, the time, and the money, then you'll find books/manuals and friends that will help with the rest! I'd go with a local motor if you can, the cost of a crate motor so to speak from a national Pontiac Engine Builder would be too much for what you are after. (for me too for that mater)
For me... it's like an escape... just me and the car... and a few beers on a hot summer night! (yes it was almost 90 here last week-end!)