I would recommend the heavier 2K3 ignition for the 300. Keep in mind that a flywheel weight can have nearly the same effect with the 2k2 ignition. The difference is the extra 35 watts of power can come in handy if you're running handwarmers etc.
Suspension wise the bikes are pretty close to where they need to be for most riders under 200lbs. Give the bike's suspension some time to break in before you spend money on suspension work. Start with sag set to 110 to 115 and run your forks up about 1/4 inch in the triple clamp.
2 strokes 4 life's thoughts are spot on for boil over issues concening the GG300 as running hot is normally not an issue unless you're jetted lean or running in deep sand for a prolonged period of time.
Whether you do the RB Design mods right away or use a LTR jetting kit you shouldn't have any problems running hot. A good practice is to run the Hi-Lo ignition switch in Lo most of the time esepcially if you concerned about over heating in certain conditions.
The stock 08 seat is actually a pretty good one and I doubt you will be dissapointed but other seat heights and densities are available from Guts Racing.
Have fun with you new GG ride and don't forget to let you KTM buddies ride it once in awhile.
Who knows you might be setting a trend.
