Remove User\Group from Local Group on a machine and add a domain User or Group
Wrote another script, this one will look for a user\group in a specified local group on a machine, remove it, then insert a User or Group.
Handy if you want to remove GroupX and replace it with GroupY, or remove a user and replace with a group, works in any combination.
If you use this, test test test as I wrote it over a lunchbreak and did enough testing to see it worked well enough and returned the goods 
Here's the link