Oh I didn't see that you wanted to set your default route as well. Are you sure you need to? The tablet should get that from the DHCP server as well.

If you are needing to set everything manually you could edit the /etc/network/interfaces file and change the iface eth0 line (and add the following lines below it:

iface eth0 inet static
address <your ip address>
netamsk <probably 255.255.255.0>
gateway <default route ip>

Then run the commands:
ifdown eth0
ifup eth0


Once again, I could be missing something obvious, I'm very familiar with linux, but less familiar with Maemo.