Can't help you with specific info, but as a fellow G-Pilot owner I am surely interested in how it works for you.
Please post your results!!
We've had ours for about 4 years now, and perhaps 25K miles of use, and in general we're happy with the way it steers our boat
... not an inconsiderable task, because it is a fairly twitchy almost ULDB "performance cruiser", and requires a lot of steering
But, the display head
on ours has been a PITA. A few of the LCD segments failed while it was still under waranty, so we sent it in... they claimed to have replaced the display, but within a few weeks (by which time we were offshore
and unable to interact with NavMan), it began to fail again. By the time we returned to Oz, it was out of waranty, and I have been reluctant to pay for a repair that would quite possibly not be permannent!
But, enough of my whining. I hope that your FET replacement is successful, and we will be very interested in how it turns out.