This is how it works on my Sig, but yours may be different.

First, make sure the gun is unloaded. Clear chamber and remove mag.

When you push the release all the way in, you should see a tiny hole on the opposite side of the button. I use a straitened out paper clip to insert into that hole. This will separate the two sides of the release/catch. When you replace it, one side goes in first but I don't remember which (don't have the gun in front of me - I'm at work). You should be able to figure it out.

Did the gun not come with the owners manual? If not you should get one anyway.

Good luck!

I'll take a look at it when I get home tonight. Thanks.

The gun came with one of the older "zigzag" mags - that's it. The guy at the shop said that the original owner couldn't find the original paperwork or the original case, so I printed one off of Sig's web site today (don't have a printer at home). Going to look over it tonight and get a closer look at the gun. I did get a glance at a P226 armorer's manual, but what I got in there just made my head hurt and got me all confuzzled (the wording there is a little bit screwy, and it's an older one). I'll have another look at that too, if I can.

Edit - forgot to ask if removing the mag catch requires anything more than a field strip. If it takes anything more than that, I'm paying a gunsmith to do it.

Edit 2 - Figured it out. Turns out there's a little "half moon" on the mag release that consisted of the pin you were talking about that I had to hit with a hobby knife (didn't have anything smaller; a dentist's pick would have been perfect if I had one), then remove the whole assembly as a single unit without, as the armorer's manual says, pressing the magazine catch inward (instead I had to leave the tension on the pin; it was easier than trying to figure out what Sig wanted me to do). 's all done now, and the catch works good as new.