I wouldn't recommend using pliers. It is fairly simple to change either clamp the slide in a padded vise and tap the sight out with a brass punch or use a sight pusher.

If you are changing out front sight for fiber optic, consider the complete Truglo tritium sight set for daytime & low light capability. Your gun can be sent back to Sig for sight installations because alignment will need to be reset to retain accuracy. If you choose to install, don't file dovetails on slide, measure new sights with a micrometer & resize them. You need to use Loctite 609 retaining compound, not regular Loctite found in automotive dept. Measure orignal Sig sight width and file new sights to fit in dovetail, then apply Loctite 609 on both sights & dovetail. You can find Loctite in industrial supply stores or ebay. Check with gunsmith beforehand that he is using sight adjustment tool or brass punch to drive in sights. A steel punch will leave ugly indentations on sights or slide. After you file down new sights, reblue new surfaces to reduce corrosion. Caution on Tru Glo...if you use GunScrubber or solvents to clean slide, keep it away from fiber optic tubes unless you want dull blurred output. I have done multiple sights using Loctite 609 and they have stayed put. Good luck