Getting started with INF mod development

I haven't begun modding anything, but I've become more or less familiarized with UScript. For code examples: Open Unreal Editor -- Find the "Actor Browser" -- Open whatever relates to what you plan on modding. As for implementing anything into the game, I've yet to actually begin modding (as I've said), so I can't help you there.

Well, the first step if I was to start modding would be to open UnrealEd (preferably with an INF Ini) make sure all mutators I like are open (you can open packeages in the actor browser) and when all is fine locate the "export all scripts" (not sure if it's in the actor browser or in the script browser) - this should extract all uc-Files into your UT directory (well in appropriate subdirectories of course).

Resources that should help with basic UnrealScript and so on are The UnrealWiki(http://wiki.beyondunreal.com/) and Epics UDN (http://udn.epicgames.com/Main/WebHome.html) though the latter one doesn't seem to "support" Unreal1 Engine anymore, much of it still applies.

As for development kit, WOTgreal (http://www.wotgreal.com/) seems to be one, can't speak for the quality though, since I use my standard editor for scripts and batch files for compiling - speaking of which be sure to READ ALL STICKIES IN THE INF DEVELOPMENT SECTION if you want to compile something for Inf. It helps - much.

Since you mentioned you know how to write code we can skip this part, UnrealScript is pretty fun IMO - though it has its spleens *cough* defaultproperties *cough*..

Since you explicitly mentioned additional weapons: something for modeling and/or animating (Blender/Maya/3DSMax or similar) and a whole lot of time - plus I wouldn't exactly start modding by making a new weapon.

Oherwise just use the search function on these and beyondunreals main development forums - or drop by here and ask, though population is thin here recently, so don't expect answers too fast..