My youngest daughter dropped her iPod right before Christmas, and we wound up going to the Apple store over here, and they replaced the entire device for $100. I'm not sure if you can opt to just have the part fixed for less, but they said that they couldn't just replace the screen where I went.
It was a 4th gen iPod touch with 32GB of space... so getting a completely new device for $100 was great... even though we wound up getting her a 5th gen a couple weeks ago (for her birthday) we were able to give the 4th gen to my niece.
Anyway... if using the home button isn't an option ATM, I'd enable the Assistive Touch and maybe hold out until the device is totally junked, and then take it into Apple and switch it out for a new one ($100!! - sorry, just... such a great deal [IMO])
If you're set on keeping the device, it's worth it. If you're wanting to upgrade (your info says you've got a 4th gen touch? Dunno how much trouble you're having running newer games... or if you're at that point where you want to get a new device), it might be worth it just to ship it to gazelle and get a new device.
If you purchased your device less than a year ago, or purchased Apple Care and your device was purchased less than two years ago, you might be able to get it replaced for free... but only if the crack was not because you dropped it or was the result of something you did...