Here is a link to K-Var
, it looks like they are having hacker troubles right now though. Most of the kits come with the barrel already attatched to the trunnion, and if you are doing a screw build you probably want have to worry about pressing in the barrel, but if you are buying a kit that has never been assembled into a rifle you are probably going to have to press the barrel into the trunnion yourself, most people use a 12+ ton press to do this, although several people have found ways around this using a variety of methods.
Building an AK is slightly more complicated than building an AR (at least it is in my opinion). but it is not that hard, and is well within the skills of most DIY type enthusiasts. The reason that you do not have to press the barrel into the trunion while putting together a screw build is that on most kits the barrell is already pressed into the trunnion and you will simply be drilling out the remmanants of the old rivets and threading the mounting holes, whereas if you are riveting you will need to press the barrel out of the trunnion so that you can buck the rivets, then presst the barrel back in once the trunnion is attatched to the reciever.