1998 Toyota Camry Transmission service confusion

Transmission problem
1998 Toyota Camry 4 cyl Automatic 167107 miles

I have a 1998 Toyota Camry, 4-cyl with about 167K miles. I have never had the transmission serviced. It seems to be running fine. I wanted to take it in for a flush. In the process of calling around for pricing, I have received a couple of varying opinions on what would be the BEST course of action. Several places said they would not do a flush because it could lead to bigger problems by dislodging sludge, etc and ultimately hurt the tranny. It was recommended that I do drain and fills to replace the fluid. I definitely don't want to cause a more serious problem, espicially since there is no appearent problem currently other than dirty fluid. Is it better to do a flush or a drain? Also, is there a difference between a "power flush" and just a "flush"? I am more confused now than when I was prior to realizing I should service the tranny in the first place.

Thanks for any and all advice.