Oh man, there are so many things to learn with PS. Overall , I would say it took about a year for me to master the software, and that was when it was it simple, PS4.

Every version they've added new features with bells & whistles that make it even harder for the newcomer to catch on to.
I know this for sure, there are tons, and I mean tons of PS tutorials on the web. I would google a few sites and pick up some quick tips to get started. For starters , I would use the
magnetic lasso. Then you can get on to using masking.

I looked up a website for you, and you might just find something useful there. It's a little hard to try and tell someone to
do this , or do that, when you're on a message board. Best thing to do is try first hand some of the online tutorials.
http://www.elated.com/tutorials/graphics/photoshop/selecting/Sorry if I wasn't much help.

edit : forgot to add link