I can only relate my experience I am not a Sig armorer.
1. Sights are removed right to left. The rear will be on very tight. Don't mar the slide in an effort to hold it tight in the vise.
2. The roll pins are what hold the block in. Same as the sights right to left for removal. Get new roll pins from Sig they are not the same as what is avail at the hardware store. Place the roll pins so that the splits are opposite. You must use close fitting pin drivers for removal. Some say to remove the inside pin first. The pins are tight. When putting the pins back in I use a purpose built pin driver. Its holding hole is made just for the Sig pins so that the pin is supported about 1/4 the length and is somewhat compressed as it is held in the pin holder.
Lots of info over on the Sig Forum.