I've converted many 308-1 Saiga's to pistol grip. Both Carolina Shooters Supply and Mississippi Auto Arms are good sources for conversion info. But info for the 308 Saiga is sparse. Much of what you see on the shotgun and rifle conversion videos will apply to the 308 model.
The 308 version of the Saiga is totally different from the shotguns and other rifle calibers. The Saiga 308 trigger group is unique. You should purchase a fire control group specifically modified for the 308 model. Luckily, the 308 fire control group doesn't have any extra holes that have to be filled in like the other Saiga models. Also, the denial plate is welded to the receiver making removal a pain. With simple hand tools, pretty much anyone can convert the 308 in about 2-4 hours. There will be bare metal exposed afterward, so you'll want to touch it up (or paint the entire rifle) with matte black Aluma-Hyde II or other gun paint.
Here's a pile of parts removed from my first 308-1 model conversion...