I think that ofp is fairly easy to mod compared to others, there are basically seperate fields of modding, some of these are:
-Mission Making
This envolves opening up the mssion editor and making custom missions of your choice, Mission editing is confusing at first but the longer you do it for the better you get.
-Moddeling
Done with a Software called O2 which can be downloaded here : -
http://www.flashpoint1985.com/breathe/mainpage.html in this software you make your own models, and apply textures/Physics to them. If you want a good tutorial on how to use this software go here :-
http://ofp.gamezone.cz/_hosted/brsseb/tutorials.htm-Animating
Animating is where you can make your own unit Animations, to make animations people use a tool called OFP-Anim v0.98 which can be downloaded here : -
http://www.aef-kampagne.de/english/feat_XAnim.htmthere are also tutorials for it if you have trouble learning how to use it, although it is farely easy to understand (i worked it out in 10 minuites so it cant be that hard ;D)
-WrpEditing/Other Island based editing.
This is making islands for OFP, the software needed for this can also be downloaded on this page here : -
http://www.flashpoint1985.com/breathe/mainpage.html -Scripting
Scripting is basically what makes the missions run, you can wright scripts for ofp in notepad and save them, then you can have them activated by a trigger in game and take effect, Scripting is basically using commands as a computer language would, e.g. c++, html etc... for a list of the commands used in scripting/mission editing and what they do & how to use them go here -
http://www.ofpec.com/editors/comref.phpif you want to try scripting though i would download Chris's ofp script editor as it sorts out alot of the problems and saves you alot of stress while mission editing you can download it here -
http://ofp.gamezone.cz/index.php?showthis=5874i hope this has helped you