Hello and Welcome to the forum Fee,
I've never replaced the ignition switch on an XV 1600 that I can remember.
The only thing I can tell you about it is that the mounting bolts for the switch have "break away" heads that break off when tightened.
You will need to drill out what's left of the head of the bolts to remove the switch from its mount. I would recommend buying replacement bolts from Yamaha in order to retain the break away feature as a way to help deter a possible thief.
The idea in using the special bolts is that a thief could not bring his own switch, quickly change switches then steal the bike.