Merging maps into different mods or mod versions is not difficult to explain, but it is difficult to explain EVERYTHING to a modder layman. If you really want to complete a project of your anticipated scale, you won't get around understanding at least the basic principles of how mods, maps and objects interact and are referred to.
Actually, merging maps is so easy I can lay out the basics right here:
Maps are simple: They will always work on every mod version (they don't really care about mods at all, actually). However, they do care if they can load all the objects that are referred to within the map files. If there's object spawners defined in the map file that try to spawn objects that the mod simply doesn't have, it obviously won't spawn anything (which is much preferable to a simple crash, however
). But the same goes for all statics, sounds, etc. used on the map. Static objects that are defined and placed, but whose .sm files are not in the current mod will not exist ingame. Things get worse if e.g. kits are defined that do not exist. Those are a crucial element of gameplay and BF42 can't handle empty kit slots well, so this usually leads to a crash. These are the single main culprits that cause maps not to run with various mods.
Getting them to work means testing them, figuring out which objects failed to load or cause issues, then either replace them or making sure the necessary files are integrated either mapside or modside.
If you are a complete layman, the above paragraph will be difficult to understand, but as I said, I really don't see any way around it if you really want to get on with your project. And as others like fook said, asking specific questions you encountered while trying sth. yourself usually leads to a way better responsiveness than general "Tell me how to do this all"-kind questions. The reasons for this are:
1) The generic questions really have been answered over and over again in various forms. I know it might be difficult to find them due to the lack of proper search terms, but this simply doesn't really make it enjoyable for experienced modders to write it all out again.
2) Generic questions always look a lot like "I don't know things, but I don't really want to bother to learn things, so I'll just ask and those gurus will surely give me a perfectly tailored solution...". This might be true or not, but it's just how it often feels (and sadly sometimes is true). It's like a schoolkid asking you to do its entire homework instead of asking you to help it solve some issue it is stumped on while trying to solve its homework...
3) Thinking about and answering generic questions simply is not much fun. It is exhausting, it is boring, and this means most people won't bother to write elaborate responses (if any).
4) Which kinda sums up all the above: Asking intriguing, specific questions that present a rare(r) and unique(r) challenge to the modder are much more interesting, even more so if there are various possible approaches. Threads with this kind of question usually quickly get a good and steady support from various people, as the bfmods creed is: Everything in BF42 is possible, you just gotta find the right workaround...and we are damn good at finding them!
Another issue is VoIP. Many people simply don't like it, some don't have it. I myself find it very refreshing and time-saving on many occasions, but modding-stuff usually is done on-the-side of other things, and talking requires continous full attention, which also can be exhausting. That's why forums still thrive.
So don't be disheartened, all of us will readily provide assistance, but you gotta go into more detail. Explain what exactly is the issue you have with merging your maps or where you need help. If you need a simple layman's How-To on how to make maps work in a new mod at all, ask just that. It's super easy:
1) Put the map .rfa file into the new mod's levels folder
2) Open the .rfa and make sure the \menu\init.con has the "game.setMapID "XXX" value set correctly. If not, change this to the correct mod's name.
3) Start the game. If it crashes on startup, there's some serious issue with the map that will require debugging. Either use the debugger or debug "light" by using windowed mode (windowed mode gives a single error message on crash, at least).
4) If the game starts up, the map will appear in your regular map list, just fire it up on local and see if the map loads. again, if it crashes during mapload, check it with windowed/debugger for error messages.
5) If the game does not crash, you'll be able to play the map. Test it thoroughly and make sure that all objects that should be there are there. Take note of missing vehicles/objects and fix the responsible files.
EDIT: These 5 steps should be enough to direct you. There really are plenty of tutorials on how to handle .rfa files and edit value in .rfa files. Debugging crash causes is a whole new topic that usually is a lot more tricky, and for that the above guideline will help: Crash issues usually are interesting and the well-known bane of every modder and everybody will jump in to help solve them.
.