just a little smoke

I recently purchased an 04 foreman 450 for my wife and kids to ride when we go back in the fields behind my house. A couple of day's ago I was following them down the road to get to the trails and when we left out of the driveway I noticed some smoke coming from the exhaust. It only lasted for about a hundred yards and then cleared up and I didn't see it do it again for the rest of the day. I started it up this morning and let it run for a good five minutes or so and didn't see a thing so I took it down the road and sure enough for about a hundred yards it smoked a little and then cleared up and didn't do it again the rest of the ride. I figure it is just the seals and just wanted your guy's opinion on the matter. The old wheeler run's great and seems to have plenty of power. Should I go ahead and change the seals or would it hurt to keep riding it until it worsens. And if I should go ahead and change them how hard of a job am I looking at. As always, I appreciate the help.