Well, as the literal translation is actually correct in Polish... it's hard to say. To convey the sarcastic meaning, I could probably say "Nie planuję gdzieś pracować" (which is then actually correct English if translated literally), or maybe "Planuję nigdzie pracować/pracować nigdzie" (I plan on working nowhere). But all those versions seem to me very strange, they would rather be confusing than funny.
No, because "planować" is very specifically "to plan".
The best translation for your proposal would be "Nie zamierzam nigdzie pracować", which is something like "I don't intend to work anywhere" or "I'm not about to work anywhere". About to / Going to are 100% thoroughly interchangeable in uses like this.
It took me a while too, but you have to realize that verbs in Polish are very, VERY unambiguous. I don't know how far you are in the tree, but there's even a whole separate conjugation for putting "I would" in front of a verb!