As far as moving a user from one machine to another. I've never tried this, so someone may have to verify that it will work before you try it...
1. Create an account on the destination Mac, with whatever username you want. Passwords should be somewhat unimportant here, i think.
2. Copy the entire /Users/username directory into /Users on the destination Mac, where 'username' is the short username of whatever account you're going to copy-- You'll either want to use root for this, or 9 to get all those little files copied properly. Or try CarbonCopyCloner. You should be overwriting the directory that you created in step 1 with all of the actual user data.
3. Repair permissions. During copying, whether you do it through root or 9, you're going to change the owner of all of these files, which will cause problems down the line. Note that you CANNOT copy the files to overwrite the new user data while logged in on the destination Mac with that username. You'll be overwriting files in use. Also, the username of the new account and the username of the old account should be the same, if the Mac knows where to look for files in the future--
It's a suggestion anyway. Perhaps try it out before you do it, on a machine that can withstand damage to the OS... i can't imagine why this would cause a problem, but you never know. Also, you will need to make sure that the two computers are using *exactly* the same OS, i think...
pnw