IMO a very good upgrade and certainly robust. Be forewarned - early models of this sight had an issue where they leaned too far back and/or forward. Supposedly they quickly fixed this.
DSA heavy duty mount is GTG. I seem to remember seeing LAV with a Short Dot on this mount.
Para stock is a pretty damn good folder, and has good sling attachment options.
I can't speak too intelligently to this, other than to say if you have a fixed stock you need the buttstock tool. Sight adjustment is with a simple cheap tool, I believe the SKS tool works as well.
The extended shelf selector/safety is an absolutely outstanding upgrade - unfortunately I'm not sure how durable this part is. It is "drop in" otherwise. The Poly hand guards are much nicer than the sheet metal ones.
Standard metric FAL mags are cheap and GTG - I would generally avoid 30's due to reliability and bulk.
The poly HG's can be easily modified with a drill and conventional swivel or with a strategically placed piece of rail.
If I were to recommend just one for serious purposes it would be the SA58 FAL Carbine PARA.