They improved the shutter on the AFDII. I have had a shutter replaced on my AFD. I prefer the AFDII since you can separate the focus from the shutter release. Being in your position buy the AFDIII. What happened with your AFD body? You can still pick up AFD bodies on eBay at good prices. The Big advantage of the AFDIII is that it will have the new firmware for the new lenses that Mamiya has released.
My old AFD swallowed its tongue, either that or the shutter broke, I'm pretty sure it was the shutter. I think I'm going to buy a really cheap AFD until the afd3 comes out and has been problem free for a little while then get that and use the afd as a back up.