did it without shooting a single bullet! it was my first playthrough as well. only took me about 3 tries as well.
it was really fun, and actually pretty damn difficult. i spent most of the time just trying to keep track of their patterns and finding new paths in shadows so i could sneak up on them. the hardest challenge was the 2 dudes facing eachother, i guess i got lucky there.
but anyway, it was a really good game, best of luck working further on it if you are going to.