Welcome to ribnet!
Also welcome to the world of "if it's got a name on the box, expect to pay double".....
Getting it out:
1) remove the entire remote control form the side of your console
it may be worth at this point taking the throttle & gear cable connections out & taking the entire lever to a flat surface like the deck)
2) undo the big nut that holds the lever in, and unclip the plastic bit of trim that curls round from the lever to underneath that makes it look pretty.
3) undo the umpeen screws that hold the side onto the mechanism, and CAREFULLY prize it off.
4) unplug the three bullet connectors that connect the lead up the lever to the rest of the snake pit.
5) On the lever itself, undo the two screws down near the hub behind the lever, this will allow the anti knock it into gear accidentally lever (big red plastic bit) out & expose the wiring & hopefully the switch.
...and here is why I say hopefully, as my two screws are absolutely corroded in. They will be drilled out hopefully in the next 48 hrs.....
In all seriousness, corrosion is your biggest issue here, do not be surprised if you end up writing off the whole box or end up with it gaffer taped back together.
Worst case (which is what happened to me) I moved the electrics to the console (and made an extension for the anti start in gear microswitch) so I could use a nice cheap "mech only" box to work throttle & gears. (I then gaffered the 703 back to gether as a temporary fix....ahem... 3 years ago).
Assembly is the reverse of this, but you will see when you take the side off the box why I suggested laying it flat!
Also worth cleaning up the mechanism & re- greasing when you are in there.
PS don't be surprised if admin moves this to the engines section)