(Before you start you need to download steam from steampowered.com) Go to garrysmod.com and go to download. It'll take you to the steampowered.com Garry's Mod page. You will need to buy it with a source engine game(unless you have the orange box or something). I think it costs like 25 bucks normally with a source. Without I'm pretty sure it's 10 bucks.
No. Gmod is only for PC
no. gmod is only for the pc.
You need to download Gmod 9.0.4c when you start there will be 3 choose unmark the Gmod 9.0.4b and your set to go and play gmod 9 online.
Gmod 10 is a pay game. It can be purchased from the Steam store at http://store.steampowered.com It costs $10
you click the shortcut icon er the gmod .exe/file!
go to steam.com here are some links related to Gmod to help you: Steam: http://store.steampowered.com/ Download stuff to Gmod here: http://www.garrysmod.org/downloads/ About Gmod: http://www.garrysmod.com/about/ Gmod fourums: http://www.facepunchstudios.com/
NO
gmod 9, yes gmod 10-no
Any Source GamePreferably CS:S as most gmod users have this
piggymoo.com has all of stargate, but I'm not sure what gmod is.
steam/steamapps/username/gmod/gmod/data/adv_dup(or something like that)/* *place dupe .txt file or file folder with dups in it, here)
No because Garrynewman has not made l4d contact for gmod but if you type gmod in google you will find Garry's mod.org and click then type l4d and it shows l4d stuff