I'm currently going through a FHA loan assumption through Cenlar. My situation is a bit different as I'm assuming the entirety of the loan from my mother.
For your situation, it sounds like, for personal reasons, you and your wife have decided that you'd both like to be on the mortgage. With that known, I think the next step is to find the cheapest way to make that happen. $2,000 seems like a huge fee for the loan assumption. Cenlar is only charging $500 for my loan assumption (plus some misc. fees). For $2,000 I'd also explore refinancing, but I don't know what you current interest rate/situation is. I'd talk to Wells Fargo and see if you can get that price down at all.