I use PSP 8.1 and PS CS2. (I own PSP10, but ended up uninstalling it because I love PSP 8.1. For me, it's a near perfect program. )

That hardest thing, for me, in learning PS was that I already knew PSP. I kept trying to do stuff the same way in both. And you need to tweak your thinking a little bit between the two.  I would think it's easier to learn PS if you don't already have PSP. No little tricks to unlearn :)

I think that which program you select is based on what you intend to do with it. My "arty stuff" (textures, frames, backgrounds) are all done is PSP. And my postwork is done almost exclusively in PS.

Melz, if your friend is willing to buy it for you, I'd say get PhotoShop CS because it's more expensive program. And the market support for it is incredible (plus tons of free stuff). You can pick up PSP fairly cheaply on your own later. 

I think Amazon has the best prices.

http://www.amazon.com/s/ref=nb_ss_sw/104-5878497-1819966?url=search-alias%3Dsoftware&field-keywords=photoshop&Go.x=9&Go.y=14

http://www.amazon.com/s/ref=nb_ss_sw/104-5878497-1819966?url=search-alias%3Dsoftware&field-keywords=paintshop&Go.x=11&Go.y=9

Oh, and congratulations on having such a nice friend:) It must have been a very pleasant surprise to find out he was going to give you such a nice treat!