If you have a shop do it... it will be expensive. It would be cheaper to have them just install a rebuilt engine.
Yes... the crank, or rotary valve seals can leak, and cause smoke... but smoke from that issue will normally clear up after 4 or 5 minutes of running at upper RPM's. Then... it shouldn't be a problem until it sits around for a while. If it's smoking all the time... then make sure your injection pump is set properly.
OK... with that said... these are 2-stroke engines, and they will smoke a little when cold, or run at idle speeds for extended periods of time. Personally... if you don't have starting issues... I would just run it. That engine can run for a long time before needing a real rebuild.
Last thing. Are you running the proper oil for a Seadoo?