There are videos on YouTube on how to replace it. Should be able to view one on replacing the digitizer as well.
If you need just the digitizer, it can be had for as little as $15 + shipping on Amazon and comes with the required tools to do the 1520 disassembly. If you need the LCD Display + the digitizer, expect the price to jump over $100 more.
The battery price will vary greatly, so you'd need to do research on which ones are legit batteries. Prices range from around $20 to $150 from what I've seen. You'll need to obtain disassembly tools in order to do the battery replacement.
It's possible to fix the phone yourself, but it can be tricky if you don't have experience with this sort of thing and you can run up making it cost you a lot more if you mess things up.
You'll want to purchase a kit for the phone that comes with all the parts that have to be disposed of and will need to be replaced when you disassemble the phone. Torque screws, gaskets, etc. all have to be replaced every time you disassemble the phone. It's a real pain, and costs can add up.
You'll also want to locate and download the service manual for the 1520 and read through it before deciding whether or not you want to attempt to do this yourself. You should be able to find it with a simple Bing search.