Hi zicka.
The best way to learn about modding and coding for BF1942 is to get stuck in and have a look around. That's how I learnt.
Download the BF1942 mod development kit. In there you will find Winrfa. This is a tool for exploring, extracting and packing rfa files, which contains all the .con files etc
I learnt about coding and modding by just reading through them files, realising what they do (or at least thinking I realised what they do!), and then I'd see 'Oh OK, I need to change that value to make the changes I want'
and sometimes.. 'Oh, that's not what I expected'.
From what I have learnt I was able to modify quite a few things in BF/DC/DCX. I believe I was possibly one of the first people to give the SU25 cluster bombs. I made a ship repair station (I think that went into DCX). I also made the DC Nimitz fully loaded with aircraft and helis
I modified one of the allied ships in someway too I think.
So studying the files, figuring out what stuff does, is the way to do it in my opinion.
Have a read of the tutorials too, you'll probably find them quite helpful.
http://bfmods.com/tutorial.php