Same one I have. El Capitan is the last officially supported macOS version on that. You can try a later version with the workarounds that are described in these forums. I tried Sierra...it ran but I didn't like the results so I went back to EC.
You can put 8GB of RAM in there and I recommend it. That...and the cheapest decent SSD (the SATA bus is a lowly 1.5GB/s) makes it a pretty usable machine.
Full screen browser video was terrible for me until I discovered the Maxthon browser. Runs video in full screen with very little issues and the fans don't go nuts like they do when I use any of the other browsers.
You're going to have to make a USB installer on another Mac if that one's hard drive isn't working or is missing. The official route is to buy a Snow Leopard DVD and upgrade from there but you don't even know if the DVD drive is working. So a USB installer is the way to go. The only other thing I can think that might be an issue is the USB installer could possibly not see a new SSD in there...that happens sometimes but I don't know if it's an issue particular to that model.