Use the search function but....
1. You don't check it you just change it.
2. Remove steering nozzel and remove the two bilts holding the cone on. It will be messy and stinky.
3. Once a year.
4. Seadoo Jet pump oil or Klotz jet pump oil. Some also have used Mobil 1 75w-90 synthetic gear oil.
5. Download the manual for step by step instructions.