Hey Kasaris, welcome back
Others might have more specific advice, but I would say your best bet is to browse through the release notes for each of the major releases in the
announcements board. At the very least check out the highlighted changelog items (since I always highlight the most important stuff), but the full release notes of course include more in-depth explanations of what you'll be dealing with.
Certainly there are a ton of new features and maps since you were playing last! Honestly though there haven't been as many
changes, per se, that will trip you up, mostly just new things to discover and experiment with. The biggest changes are probably that removing processors now destroys them, along with a big rebalancing of propulsion, machine functionality, volley timings... all of which are basically in your favor and work to make the game both a little easier (more streamlined) and even more fun. So you'll probably do better that before, even without exploring all the details beforehand!
Good luck!