yeah, the drums are worth it mate. I've got the guitar hero brand drums and they work nicely!
Some of the hacks just require a wad installed and then you can download the songs direct from the games - just go through and get the ones you want.
The other idea (what i did) was to get all the song files.
You can get a program called "rock band song manager" -(I think) and you can manage the songs from your PC and SD card easily - as SDHC isn't supported, you can quickly fill up a 2GB card!
Have fun.