I always have extra screws/bolts when I take my car apart and put back together. It's called being efficient.
Granted, I look at stuff like this differently than many people, but I'd rather fix stuff myself than deal with shipping and waiting etc. After all, I did take my Bullboss apart and start working on it the day I got it, haha. As long as you don't do anything crazy, I'm sure I or someone else could tell you where those extra parts go Once you figure out how they work, they really aren't that hard to take apart, and you can download the parts diagram straight from Hatsan to help.
Yes Trinh have my Nova arrived yet? I'm wondering if Hatsan use a standard size bottle and if regulators for other bottle guns are compatible with it.
There is no reason to take the side cover off at all, unless you're having problems with the magazine indexing, which doesn't happen much. In other words, leave that alone, haha!
The transfer port is tight, because it is probably bound in place by the cylinder carrier. If you loosen the big screw on the bottom of the trigger tube that the stock screws into, then the big brass cylinder carrier will have some wiggle room and the transfer port will come out much easier then. That big screw holds that cylinder carrier in place, along with the front breech screw that is removed when separating the breech from the trigger tube. Also, polishing the trigger tube and hammer really isn't necessary, and you'll only gain the effort in doing it
When you say breech o-ring, I'm assuming you're talking about the o-ring that seals the probe in the barrel, right? The best way to do it is to pull the barrel(2 set screws). The end of the barrel where that little o-ring is, actually is a cap that screws off. When you screw that off, the little o-ring is easy to replace. Looking at the barrel, you'd never know that. I didn't know it at first either, but Norman showed me back when I was just getting into this stuff. Some are tight, and some will come off pretty easy. I had to use pliers and some cloth wrapped around it to get it off. The edge of the cap stops at the first of the two o-rings on the outside of the barrel there.
Trinh told me on Facebook he's sending the Nova back. He's disappointed in the finish, says it's rough.