I have done remote upgrades before, but its been a long time. So after I backup the system, then use the DM's file utility to upload the new files, and dump the old ones, and reboot what happens next? I plan to do this remotely, Will the IP address/password stay, so I can get back into the system and get to upload the database?

Does the embedded voicemail files/recording not get erased when you perform upgrade?

Do ver 4.6 cards need a separate firmware upgrade for 4.75?

IP address will stay, password will default. You can get back in to upload the database. You can leave the voicemail files as is and then you wont lose any recordings.
You shouldn't need to upgrade any cards, maybe OAS or PRI things like that.

What model system are you upgrading?
If 7200 2 cab or 7400 you won't be able to upgrade the lcp/lp40 remotely

Its a one cabinet 7200S so sounds like I should be good.