Need help on a 88 gmc tranny

I lost reverse on my 88 GMC pick up. I have a 700r4 in there now and was wanting to know what has to be done to put a th400 in its place. I am basic at mechanics at best(I could remove and replace, but heavy alterations I can't do) The cost to rebuild my tranny in this area is over $1200.00 and I could get a decent th400 for $200.00. Any help or suggestions would be great.

Thanks Everyone....

[c_rock]

You need to post over on the Chevy board. I don't think it will be too difficult of a swap, but haven't ever done it, so could be wrong.