Game cache natives are still fully functional as far as the game is concerned.
The broken GUI actions can also be fixed with a custom GUI action list.
JASS will probably take a few months to learn, but is the only way you can ever make a map of high quality for multiplayer. I advise you start from the basics, looking at the pattern of jass code as syntax is highly important with programming. Case of the key words is also important, I advise noting them mentally as well.
Remember game caches only retain data after map end in singleplayer, so you will have to use save/load string generators for multiplayer maps.
I advise getting a program like jasscraft or jass shop pro for an easy to use native list and using JNGP (jass new gen pack) for better jass support within WE.
If you already know a programming language, it should take a matter of hours before your first scripts are running ingame, although they may be a bit simple.
