pictures of jigs are in the tutorials. The middle of summer is slower here due to people playing outside. You'll get a better response once fall arrives. Most jigs are merely some channel with washers and all thread rod with a few nuts to hold things in place. That, a piece of fishing line or string, a level, and a straight edge, and you've pretty much got everything you need except a few dimensions, which are also available in the tutorial section.
Plans are dependent on the whether you build or buy a grip or bolt, or for that matter, whether you buy receiver halves or torch cut pieces. There is no single set of directions that work for all cases.http://www.robertrtg.com/store/pc/MG42- ... iewAll=yes
RTG (link above) has some pieces for building, including rivet jigs, bolts, receiver parts, and grips, as do other places online.
A lot depends on what you want to do, and what you have.