How different are the Arabic dialects from MSA?

I plan to start Arabic soon in college which means they'll teaching MSA. I want to learn the Maghreb (specifically Moroccan), Egyptian, and Gulf (specifically Iraqi) dialects. How different are they from MSA? I know that the Maghreb could be hard to understand but how long would it take to learn them? After, say, 2 semesters of cles would i be able to unserstand any of the dialects?