This is probably a question I should already know the answer to, but I am going to ask it any way, just to be sure.

If I purchase an 8700g that is unlocked (I already have an 8700c) then all I have to do to use the 8700g is remove my 8700c's sim card and put it in the 8700g, correct? The phones are similiar as far as network and such.

Thanks.

Yes, just move your sim card from the 8700c to the 8700g. Make sure is unlocked so you don't have any problems.
I purchased an unlocked 8700g from one of the forum members and I am really pleased with it. I suggest you browse our Buy-Sell-Trage section.
Now, remember to change your handheld in web client or BES which ever may be the case.
Hint-
When I received mine eventhough it was brand new, when I tried registering in web client, it said that the handheld was not intended for this network or something like that. Just turn the wireless on on your new device, let it register on the network and then try to set it up again in web client. It should work.