getting a different photo in a sidebar depending on the page is a lot different than having different widgets in the sidebar depending on the page.
If you want a different photo on different you could use something like nextgen gallery.
As for learning it all...big subject. My suggestion, make a test wordpress site and play with it. Try each of the options and see what they do. You can also take a class, but if you're not going to DO development in PHP, it might be better to find other ways around your issues, or change your needs (this is much simpler). Ask yourself, do I have to have 'X or can I live with 'Y'.
there are some great site out on the internet and some big money has gone into making them. Flynn has given all us little guys a leg up. (ok, I'm not a little guy, I've been playing with computers, mainfranes to pc for 30 years. I did tech support and picked up quite a few computer languages over the years. While I can look at the code Flynn has written and figure it out, I'd rather live within my limits until I can find a way arround them - case in point, I like rotating images, found some code, Flynn put it in, BUT I'd really like to use NextGen Gallerys but I can't figure out how to make the tops of the image box rounded. So I'll live with the current method until something else comes along.
Sorry for the long rambling answer