I see there's a MOD for the user admin panel to do multiple selections, is this the best way to get rid of a bunch of spam accounts? Any other alternatives? I've never done any MODs but will try anything to clean up the site.
Use the Admin Toolkit (link in my sig).
It's a single file you upload to your server, you don't have to change any of your phpBB files.
It can sort users by "activation", number of posts etc. and delete them in batches.
I installed the User List MOD last night on a test forum that I have and it worked great. I was planning on doing that on my real forum tonight but your Admin Tool script sounds cool. I'll try it and see...