I have a 48qt Igloo Ice Cube, but it doesn't have a spigot on it.... is there any issue with drilling one myself, and is there anything I should do in order to make it actually work.
You should be able to drill a hole carefully and it should work fine.
When you put the plumbing through the wall you're going to have a flat washer on the inside and outside with an O ring behind it. I would assemble all the hardware and use the flat washer for a template to know where to drill. You don't want to end up with the hole to low so that you can't fit your washer on without having to cut it.
To get a good/safe seal, I would suggest using high temperature O-rings from an auto parts store behind stainless steel washers. This has worked great for me.