You can make your own hud by using some software.
I think you should search for GIMP.
Also there are some tutorials on these forums go look for them.
You can make a multiplayer game by looking into the manual.
Its very easy, and you dont have to read that much.
For making a single player & multiplayer game you have to
own some particular program.
For example: Auto play media studio, Visual Basic.
Both cost money...
Since FPSC doesnt have this action.
You should make 2 games (1 single player, 1 multiplayer).
And put them together in 1 map, then "compile" them with the
programs i just named.
I am not going to make a full tutorial overe here, so you should
check their site out.
And maybe there are some tutorials on these forums.
Cheers,
Cheese Cake.