I have a question for you, do you know how to use a modelling program (3ds max, maya, blender, gmax, ect.)?
If you said no, you will need to learn how to use one, also you will probably want to learn how to use image programs to make textures. You can learn by searching a tutorial on youtube.
If you said yes, then try to get help from other forum members. I would also recommend downloading the Halo Scripting Bible or whatever it's called. Look up tutorials for multiplayer maps, this should teach you how to use the HEK (halo editing kit), guerilla, and tool. Some things are different between sp and mp maps (one of these is scripting knowledge). I'm sorry if my response didn't help you much, I'm sure other
helpful members of the forum can help you.
Links to programs mentioned plus some (thanks for doing my work Yoda)
Quote: Posted by Yoda
3ds Max (I use 2010, but you can use whatever version you like)
(simply register and download student version)
GIMP (like photoshop, but free and open source)
http://www.gimp.org/downloads/
Audacity (for making/editing sounds, also free)
http://audacity.sourceforge.net/download/
Halo Custom Edition (I assume you already have this)
http://hce.halomaps.org/index.cfm?fid=410
Halo Editing Kit (HEK)
http://hce.halomaps.org/index.cfm?fid=411
Kornman's HEK (optional)
http://hce.halomaps.org/index.cfm?fid=1081
Project BlueStreak (all three downloads)
http://ghost.halomaps.org/bluestreak/
CADs Animations Exporter
http://hce.halomaps.org/index.cfm?fid=3627
{TLS} Udie's Sound converter (optional)
http://hce.halomaps.org/index.cfm?fid=2659
Blender is an amazing program but it is not very well suited for Halo at this point in time. In addition to that *most* people agree that it is not very user friendly. 3ds max can be used for free with a student license (provided you don't use it for commercial purposes, but modding is fine).
I'll add the scripting bible too: http://hce.halomaps.org/index.cfm?fid=2809
Hope this helps somehow.