Actually, that picture is an 88. They are rare and the only year that had a clamshell seat assembly, hinged at the rear. The 89 had a removeable seat like they all do now.
http://www.seadoosource.com/seadoomodelreference.html
Chester
Yes, you need a new MPEM. You can verify this by disconnecting the wires to the MPEM and checking the resistance between the fuse and the ground wire on the MPEM.
Chester
Yes, you will have to intake remove the manifold from the engine and remove the gear first. You might find it easier to remove it with the rotary valve cover and then take it apart.
Chester
Remove the head and inspect the pistons to see what size they are. If they are first over (.25mm) you're OK. If they are .5mm over, shave the valves by .005". Take .005" off for every .25mm they are over the first overbore.
Chester