Well, hope you make it to the shoot, lunde!
As for the +p+ question, I've scoured the literature for anything that might shed some light on it, and the closest thing I could find was the manual's statement that:
'only good quality factory ammunition should be used. If you prepare your handloads be careful, and do not exceed recommended pressures in line with those generated by standard factory loads (not +P) as manufactured by Remington, Winchester, Federal, Hornady, PMC or other reputable companies.'
You could read that to mean factory ammunition, including +p or +p+, is okay, but handloads should be restricted to standard loads; or you could read it to mean that no +p or higher pressure loads should be used, including factory ammunition.
However, keep in mind that it is a modern 'service pistol,' and that it is intentionally overengineered. I imagine that firing a box or so of high pressure self defense ammo, say, for example, 124 gr +p+ Win RA9T, just to make sure your carry load functions properly, wouldn't hurt it...