1. You need a good and free stock photo website. Most of these sites offer high resolution photos for free and without restrictions (remember to read the terms thoroughly though, just in case). Try
http://www.sxc.hu/ and
http://www.morguefile.com/ for starters.

There's also DeviantART too, but taking stock photos from DA requires you to sign up for an account and post your finished work with credits there (ie. for DA use only).
2. I love the idea/concept of the artwork. It's not easy to operate Photoshop at the beginning... for me that is. When I first got Photoshop, it took me another 3 years to actually summon up the courage and learn it.

But once you get the hang of it, every thing just falls into place like magic.
3. Practice, practice, practice. And looking up tutorial sites work wonders too! I'm still learning new things as I write this.

I don't know everything about Photoshop, but I'm happy to give you help/tips/pointers... dont be afraid to ask/PM me.