Moving out of windows laptops and need some help

I am replacing my HP TM2 as my school laptop, and i'm either going to a MacBook air or an ipad 2. My experience with apple products are either a decade old (my family had an imac 3g back in the day) or where had at the demo MacBook in best buy. I have a few questions I need answered before I move out of my windows laptop. 

1. I have an android phone and a windows desktop. I know the MBA can, but can the ipad function in an otherwise apple-less world? 

2. Is "notes+" (or any other note app) for ipad strong enough to replace Microsoft onenote as my note taking software? 

3. How long does it take to figure out OSX, coming from windows? I was a bit confused about some of the bits and pieces of OSX in best buy. 

4. Is there any one stylus for the ipad or "must have" accessories for the MacBook I need to know about? 

Im not getting rid of my gaming PC and I still like android more then iphone, but the windows laptop experience is infuriating for my purposes. I keep up on apple news because its obviously a big deal, but I have no idea what actually owning an apple product is like. If it where a toy or a secondary device I would just jump in, but I will be depending on this thing from day one. So I need to look before I leap. Sorry for being a bit of an apple idiot, thanks for the help!