the 1911 is easy, the sig not so, I have done some, but just for my self, working on a set for Hi Standard Victor at the moment.
If you are not a wood worker, no tools ?, if you want to learn, go ahead.
you should have a band saw or fret saw, carving tools, spoke shave is handy. Also good quality rasps are a must1/2 rd
When you get into some if the semi auto 9mm, it is what is on the inside that is a pain, as the inside of the grips hold things togerther.
Then if you get this far , you should get some checkering tools
Main thing is take your time and don't rush.
If you think these are a evening job, you will mess up.
BTW, something I have found, cut your wood about 2 or 3 times longer than the grip, than you have something to clamp in a vice when your are working it.
Then just cut off what is not grip when done, I use tong oil or true oil