Welcome to TTF.
Before doing anything, please make an Explorer, not Home, backup of your unit's contents. If not sure how, see here:
https://www.tomtomforums.com/genera...4-how-backup-contents-your-unit-computer.html
Once that is done, you should be able to get the newest USA_Canada_Mexico map using the Latest Map guarantee. The most recent map is 860 and was released about 12 days ago.
You should be able to install the map (it first downloads to the computer and installs from there to the unit) without having to delete any voices but, honestly, some are having space issues.
You may try to avoid that by (before getting the LMG but AFTER the Explorer backup) connecting to Home, Manage Unit, Device tab, voices, expand, and remove any computer voices that you won't be using. The recorded voices don't take much space up, the computer voices do.
So...................
I'd try to do the map update without removing voices. Be advised that the usb chip in the 540 is only 1.1 compliant, not 2 (*believe it or not) so the install will be slow.