re: "...[the dealer] ... pointed out that Volvo does not recommend a trans fluid change interval! I am astounded, just says to check it every 10K miles....
The fluid looks a light brown color, does not have a burnt smell to it...."

First of all, the dealer would love to sell you some transmission work another few years down the road -- he has no incentive to help you avert such a job in the future, so why trust him?

And certainly, your fluid is the wrong color -- brown is bad! It means that it has oxidized from heat, etc. It should be flushed!

You can get a flushing kit (basically a hose with the right fittings on the ends) from IPD. And you'll need the right wrenches -- make sure they're flare-nut style, for the safest handling of the line's nuts so you don't "round" them.
Yes, others may suggest cobbling your own hose (instead of paying IPD's price), but I'm not sure how experienced you are (based on your questions, but no offense is meant), so the easiest route is to get IPD's kit. And you'll really feel good seeing the new Cherry Red color of your tranny fluid once you've done it yourself!

Good luck.