I've looked through the IRF710 Datasheet:

http://www.vishay.com/docs/91041/91041.pdf

However, the datasheet does not specify what pin the tab is connected to. I'd like to know this before I finish ordering a heatsink, if it's connected to the drain, I'd need some sort of insulator, correct?

What pin is it connected to internally? Is it floating?

Thank you.

 

The IR version shows the Drain as Tab connection.
You could also do a resistance check.
Max.