Sticking in reverse

I have a 1998 Mazda MPV sport which I bought used 2 years ago. It now has approx 9,800 miles on it. It is an automatic and I am having problems shifting from reverse. It either sticks and I have to force in into drive, or it shift just fine. What do I need to know/ask before taking it in to a mechanic?

I know nothing about cars, Please Help!!!

Correction, my MAzda has 98,000 miles on it. Leslie Sparks

Just a wag, but you could check the fluid level. Also, when was the last time the fluid was changed in the transmission? I beleive this van calls for transmission fluid change at 60,000 miles. To properly check the fluid, drive the van until warm, park on a level surface, and, with the engine running, pull and check the dipstick for the transmission.