Another engine/trans question

So it turns out I was too impatient - again. I gave up on my current 289 too soon. I just got it checked out, and the reason that it was weak was that the distributor wasn't advancing the timing at all. Doh!

Anyway, I still need to do something with my transmission. I found someone that I feel is a good rebuilder of C4s. He has been building mainly C4s since the 1970's and he will get me a rebuilt C4 for $600. Good deal?

Now... here are some more questions regarding the transmission work needed:

Does it make sense to put a rebuilt transmission behind an older engine? I'm not sure if the 289 I'll have in front of it could do any damage to the transmission. My goal will be to put a different engine in there eventually, but if the 289 is good enough for now it is staying (due to budget).

Is it possible to remove and install a transmission w/o pulling the engine?

Roughly how much would I be looking at (cost-wise) for a shop to install just the transmission? What about the opposite... how much to remove the trans?

The guy who will sell me the rebuilt C4 doesn't do any installs anymore, so what I'm thinking about doing is getting my C4 removed at a shop, drive it to the rebuilder and pick up new C4, drive that back to the shop to install.

Thanks!

Nah, I decided against AOD.

There are too many mods necessary to the car overall, which equates to more dollars spent and more time wasted.

The guy that will build my C4 is positive that they are strong enough, if built correctly.