I'm thinking of getting into helis and, after four years of flying airplanes, I understand most of what I read about them. I just can't figure out what "tail in" or "nose in" means? Probably a stupid question but can anyone help? Is there any other lingo I may not understand, being an airplane pilot?

Tail in and nose in are referring to the orientation of the helicopter in a hover. Tail in is when the tail of the heli is facing you, you're standing behind the helicopter. Nose in is when the helicopter is facing you with its nose.
Tail in hover is the first maneuver to get down. Once you're confident you can get into side hover and lazy eights, then figure eights in front of you, then probably forward flight which should be easy for you since you've been flying planks. Then probably try to nose in. It's hard for any pilot, but especially for plank flyers converting as they're not used to the fact that the helicopter is coming at them, yet it's standing still