Cloud One has given you the most accurate information. The quote above says you will just have a spare account - that is not the case. Ganz will close that account when they re-set your pet code.
I had done this a while back and I had 2 pets on my account. I also had a few charms on the account but they were not transferable. Almost everything IS transferable via Kinzpost like the others have responded. You can not Kinzpost anything that you bought from the e-Store and put on the account you want to close ~ like the charms I had gotten.
I did use up all the money I had and bought higher priced items and stuff from the Curio Shop and sent it to the account I was keeping. Make sure you do send everything you have to the account you are going to keep or else you will loose it. The one great benefit is that you will get the PSI
twice, but I decided that I wanted everything on one account and not separate accounts. So having 2 of my pets items was a good thing and made up for the items I couldn't transfer.
Good luck with your accounts and enjoy the extra PSI!!!
I don't regret putting my pets on the original account I had, I am glad that I was able to get the code reset.