First of all, congrats on the G29, and welcome to GlockTalk! IMHO, you have the ultimate carry firearm, It's what I carry!
Secondly, shoot the darn thing, and without hesitation, use underwoodammo. Examine the brass around the base, above the extraction groove. If there are pronounced, bulges, an after market barrel may be in order. If no bulges, factory barrel is good to go!
After shooting a box or two of underwoodammo, notice the ejection distance of the brass. If it's 4-10 feet, never mind a new guide rod, and spring set. If the ejection, is greater, perhaps something in the 20-23 LB spring weight is in order. After you have run a box or two of ammo through it, and decide you need a guide rod, and spring enhancement, let us know, and I can tell you what I've went with.
As far as other add ons, for the most part, it's just spending money, that could be spent on ammo.
Lastly, save all your brass!!!!!!!! It is gold!!!!!! If you decide to ever reload, and you should, you will be glad you saved it. If you don't, people will be willing to trade good things for 10MM, once fired brass.
Go out and run some rounds through your G29, then get back with just how effing cool it is to shoot!