For the benefit of anyone doing a search. Here's what I did...
1.) Shut off my phone.
2.) Took out the 2GB card and stuck it in an SD adapter, and stuck that in my MacBook Pro.
3.) Put the new 8GB card in my phone, then turned the phone on.
4.) Plugged the phone into my MacBook Pro via USB, and enabled USB on the phone's screen.
5.) Selected and deleted everything on the phone's new 8GB SD card.
6.) Copied everything from the 2GB card to the phone's new 8GB card.
7.) That's it. Everything seems to be working great.
I wasn't sure if it would work on a Mac (only because every Android tutorial I've seen for anything people are using PCs), but it worked great.
Not that I am surprised that the above worked, it's exactly what I expected. But I wanted to share it none-the-less for anyone who a.) might think it's more complicated than it is, or b.) might have a Mac and is unsure if they can do this stuff on a Mac.