Engine / Transmission swap - explain it to me like I'm 5

[hjl]

I recently picked up a 71 2WD Blazer. I had set aside a certain amount of money to buy it, and only spent half. So I've still got some left over, and I'm trying to decide how to best spend the money to fix it up. This will never be a daily driver, more like nice days, weekends, going for the paper or ice cream.

The body is decent, don't really need to do anything there yet, even though I might want to change the color eventually. I really want a custom roll bar, but that can wait, too.

It looks like it has the original 6 cylinder engine and three speed manual transmission. When I first drove it I thought I might need a carburetor rebuild, but now that I've driven it a lot more I think both the engine and transmission might be nearing the end of their life. So I started reading threads about engine and transmission swaps, which is dangerous to my wallet.

I can't do this work myself, but I've found a couple local mechanics with very good references who might take it on. I want to understand the process, and get a better idea about the amount of labor involved.

Can someone explain it to me like I'm 5? Here's what I've learned by reading threads on this forum:

1) A nice crate motor, automatic transmission, and various other parts needed can be purchased for around $3,000. Is that right? I looked on jegs.com for those numbers.
2) There's things attached to the frame called crossmembers which support the engine and transmission. I would need a new crossmember to support the automatic transmission, and the old crossmember removed. I would need new engine mounts to support the new engine. Is that right?
3) A torque converter fits in there somewhere, I think it's attached to the flywheel of the engine on one side, and the input shaft on the transmission on the other. Is that right?
4) I'll need a new or modified drive shaft?
5) I'll need a way to shift, either a new steering column with automatic shifter, or a hole in the floor with shifter sticking through? Does it make a difference?
6) The new transmission has fluid which needs to be cooled, which might require a new radiator if mine doesn't support cooling a transmission. Is that right?
6) What major things am I leaving out? I guess things have to get wired up differently.

Considering all of the above would take me close to 6 years, I have no idea how long it would take a skilled mechanic. Can anyone give me a very rough estimate on hours? Am I correct in assuming that rebuilding my current engine and transmission would be similar in cost, maybe slightly less?

Thanks in advance, sorry I wrote a novel.