Well actually that site has disassembly and reassembly instruction vids
here. I'm sure you could probably find some disassembly vids on youtube or the like as well.
Here is a step by step but the picture links seem to be busted.
It wasn't too hard to take apart and put back together my 8320, it just takes time and patience if you're not used to doing things like that as there are some fragile pieces that can break (for mine there were small tabs that kept the left and right sides in place which snapped off when I was taking it apart though luckly I was replacing them anyways). Also you'll need to make sure what tools you need, mine needed two different sized hex screwdrivers, and I also bought this double ended pick thing to easily push the tabs and separate the housing.
As for recieving them, the case came from China I believe, and it took about a week and a half to get to me in the US.