Wow, talk about twins, I got my '03 K1200LT 3-4weeks ago. I always wanted a V-max and a BMW LT, My wife finally allowed me to fullfill my first and second mid-life crisises (Still waiting on my pre-'72 Vette).
I'm 5'11 with a 30" inseam. I just have to say. in the first two weeks, I layed her on the right side 4 times. But it was always on walking back or once coming to a stop on a slanted road. Thankfully the black front 'bumper' and the chrome on the side bag (underside of it) seem to take minor damage at a nearly stopped speed. After 5+ mph, the LT just is smooth as glass. I still working on practicing my slow speed turns in a empty parking, as advised by my Gold Wing friend. But as a E-Glide owner, I think the transistion will be ALOT better than mine.
I also have the stock Gamin Navigator III. As for upgrading, it'll depend on your computer. (Assuming you have the original cables) If you have an old computer with a serial port, you are in luck. If not, you'll need to order a Serial to USB converter. I bought one a few weeks ago for about $18. Then you'll need to register with garmin and upgrade your maps. Navigator III was supposed to have lifetime free upgrades, the last upgrade I was able to find was late 2008/ early 2009 (not great but was ALOT better). I think the biggest key is having all of the codes and keys. I was luckly that my previous owner included all of the paperwork and numbers. I personally plan on upgrading to a Garmin nüvi 2360LMT next month when it comes out. How I'm going to intergrate, God only knows.
As for seat height. Even at my height I sometimes have trouble 'flat footing' on the ground. Granted I live in south Louisana, so we tend to have some driveways road combos that aren't ideal. IE, while you front tire is coming off driveway, you rear tire is coming up the road. So I'm on my tippy toes at that time. A friend of mine bought a lower seat, but he said he had to modify the under the seat. I.E. He had to trim the panels under the seat to allow it to sit lower. I'm sure there is more than a few guides out there on how to do it. I plan on geting some bigger soled boots for riding.
Sorry, I didn't relize this was turning into a rant.
Also the is a "Hall of Knowledge" under the tech section that might also help.