Set Primary Group and Delete All Others

Hello PowerShell Gurus,

I would like to write a script and need some help. I am still in the beginning stages of learning scripting. What I would like to do is this:

1. Search through an OU and find people that are members of "Domain Users" && total group memberships is greater than one
2. Set Domain Users as the primary group and delete all other groups

Any thoughts would be greatly appreciated!

Thanks in advance