Hugh, that was WRONG! But funny.
VaSteve, go here, and do your homework:
Command-Tab » Blog Archive » Upgrading iPod Hard Drives
You can actually go all the way up to a 240G hard drive!
You will need a thicker back, as the 30 gig hard drive is thinner than the 80. I used these parts. It says it's for the 60, but it works with all of the 8mm thick drives :
Front Back Cover Panel Housing For IPod Video 60GB BLK - eBay (item 370223892561 end time Apr-28-10 14:37:57 PDT) Great people to deal with too. This comes with the pry tools to open the ipod. You will have to use the headphone jack, battery, and Hold switch from your old back plate (see the videos posted for Hugh). It only takes a very small phillips screw driver, and peeling up some two sided tape on the battery. If the battery is weak, now is the time to change it, or to upgrade to a higher capacity battery.
Then you will need a hard drive. I used this one:
http://www.amazon.com/gp/product/B0010HVWJA?ie=UTF8&seller=ASFHOWYNTGRQ6&sn=ESI%20World
It really is just plug, and play. Just be sure to back up all of your music.
All of these parts are for an ipod Video 5G so they may not work with your model.