I've got an armorer's manual for the PSG1 in pdf. But there's one caveat - it's geschrieben auf Deutsch. So if you can't read German, you'll have to type a lot of stuff into babelfish.
However, it does have some good pictures, exploded views of the trigger pack that should help. It's on p.24 of the manual, or pdf p. 25/37. It's really no different than an SEF pack except for one thing - a little tab thingy they call a 'finger' that goes on the sear spring shaft. If you can do the SEF packs, you can do this one.
Shoot me your email address and I'll send it to you.