Just to pile on what has already been said.
Get a suppressor that can be taken apart by the user for cleaning/maintenance. You will NOT regret spending a few extra bucks on this feature.
If legal in your state - absolutely go the "Revocable Living Trust" route to purchase the suppresor, and any other NFA items. guntrustlawyer.com has lots of info here and can help you set up a trust. (You could also go with Quicken Will Maker software, but many folks discourage this route)
At least take a look at the Tactical Innovations Quest model suppressor. It is a LOT of suppressor for $399 retail. I own one and can highly recomend them.
I am not a fan of the Walther P22 as a supressor host. Although many, many folks use and like them. I strictly use Ruger MK II/III guns as my .22RF suppressor hosts. Ruger now produces several .22 handguns that are factory threaded.
Lastly be patient, this is a process that takes months from beginning to end. Right now in Georgia it is taking right at 8 months to get Form 1/4's back and that is using a "Trust".