Anniversary is an adventure to change corks. The whole rear end basically needs to come apart to get the drive out. They are not greenfieds finest model to work on.
If you shop around you, keep an eye on marketplace and gumtree, you can usually pick up nice models under $1000.
The 8" rims will fit, but the tyres will hit the guards and throw you're cutter deck angle way off, as they are substantially taller. You would need to change the fronts as well, but they will hit the deck when you turn.
