Sure it can be replaced w/o pulling the tank. Open the fuel door, remove the fuel cap, grab the old one with some pliers or Vice Grips. (I use a 6" pair of needle nose) and pull it off.
Good time to remove the door and clean out the recess with some wax/cleaner and make it all pretty.
Spray it with some Silicone spray, makes it easier to get it over the filler pipe and seated in the grove where it fits around the sheet metal.
I just replaced one last week. got it from Phill with an order. 123 997 35 81, or Fast lane part# W0133-1639171. think it was around $2.64.
Charlie