I have had a SJC gun since 2007. Mine was one of the early ones before the screws in slide plate. I had to have the barrel replaced and John completely rebuilt the top end for me that included comp,barrel,extractor w/adj screws,striker. Two of the three allen screws are to hold the plate tight to the slide. The one for the extractor is for adjustment. To remove the plate from the slide you need to count the number of turns on the extractor screw to loosen and then loosen the other two. Keep track of your count on the extractor screw,because you need that count to tighten that screw for the proper tension of the extractor when shooting 9major. The comp can not be removed unless the barrel is being replaced. You have to clean the slide and barrel the best that you can with the barrel still in the slide. I would'nt worry to much about the comp as long as you're shooting jacketed bullets. Cleaning of the comp should only take wiping a cleaning patch with solvent through the ports.
I reload for mine and cleaning is fairly easy. I just run a rope snake through the barrel 3 to 4 times after shooting. The only time I strip mine down completely to clean is if I shoot some dirty shooting powder reloads or cheap factory 9mm ammo. Otherwise I shoot it like I do some of my other Glocks.