To get rid of it (temporarily, no longer appears in the menu but you can call it from the command line still)
sudo mv /usr/share/applications/op_pndstore.desktop ~To restore it to the menu
Code:
sudo mv ~/op_pndstore.desktop /usr/share/applications/
To get rid of it less temporarily (can still call from command line but no way to get it back into the menu)
Code:
sudo rm /usr/share/applications/op_pndstore.desktop
To get rid of it permanently (should free up a few K on the NAND)
Code:
sudo opkg remove --force-depends pandora-pndstore
To reinstall it requires an internet connection
Code:
sudo opkg update; sudo opkg install pandora-pndstore
NOTE! I haven't actually done this, there are other packages that claim to be dependent on pndstore and doing this could break things, or they could just be paranoid about their dependency and don't actually use it at all. If you do go through with the remove, worst case you'll need to reflash. Most likely case is that you'll simply need to reinstall it.
edit: incidentally, adding new items to the menu is as easy as creating a standard
.desktop file and dropping it into that /usr/share/applications directory.
edit edit: to answer your other question, if you have some small PNDs you can put them in /pandora/menu or /pandora/desktop directly on the firmware and they'll show up, same as any other PND. The NAND is very very limited though. Also things that are normally written to appdata on your SD will be stored to the NAND as well. There's room for pndmanager.pnd on the firmware, but it does a lot of writing every time you refresh the package list, so probably not a good idea to keep it on NAND.