I locked myself out of the UI on one of my Dell switches today. I spent 20 minutes looking through Dell manuals until I found the answer.
To change the management IP of a Dell switch:
Console# configure
Console (config)# interface vlan 1
Console (config)# no ip address (Removes the existing IP)
Console (config)# ip address [IP] [subnet mask]
Console (config)# end
Console# copy run start