Spark plugs vary by model year, there is a detailed write up regarding spark plug use at:
https://www.facebook.com/groups/ChaparralVortexBoatOwners/permalink/2424043411234730
Regarding recommend oil, the manual for the Rotax engine specifies BRP XP-S 4 STROKE SYNTHETIC BLEND OIL GALLON, Part# 293600122 (5W-40) as the preferred oil, and if you wish to play it safe, and be conservative, this is what we recommend you use.
If you wish to try another brand, Shell Rotella T6 5W-40 is highly recommended by many, including the author, but it’s up to you if you exactly follow the owner’s manual or not. The Rotella oil is likely superior, but some folks feel safer sticking with the conservative factory recommendation.
We recommend you use only the newest Rotax oil filter, designed for the ACE300 engine, and resistant to collapsing under pressure. The BRP part number for this filter is 462482, Sea-Doo part 420956744.