Is this going to be like a centerpiece with a real pumpkin fall motif? Do you want the rings and the Happy Anniversary in the vine carved into the pumpkin? Or just the rings carved in with some thing around them carved, and then around the base of the pumpkin, have a vine with some letters?
If you just want to have the rings carved in, you could put the pumpkin on a pedestal or small plate/dish then you can some letters from the craft store, even cut them out of heavy card stock to look like block letters. You'd have to do some measuring. Whatever kind of letters you want to use. You could ever paint the pumpking with a shimmering gold paint and use flowers around the base of the pumpkin with a pick that says Happy Anniversary with ivies and vines around.