well after learnign as much as i could about your car, i learned two things, 1 being, im never buying one, the seoncd being it has two motors.
If you have the 130hp model with dohc, the spark plugs will be located directly ontop ot the engine recesses deeply between the two camshafts, they will not be visible on the side fo the engine or anywhere.
Obviously you need th spark plugs, once you have them, you need to gap them, your owners manual will probibly have the spark plug gap listed, you need a gapping tool to do it, they cost like $1.99 at any tool store
First you probibly have to remove some kind of plastic covering, that will expose the valve covers, it should be easy to remove, once you see the valve covers, you need to pull out the plug wires from the holed inbetween them, they will be long rubber rods that fit down into the holes and onto the spark plugs, there may be some kind of additional plastic peice protecting this area that you will have to remove to pull out the wires.
Try to change the plugs on at a time and only remove and replace the wire one at a time to minimise the time the plug hole are expose to incoming falling depris.
After you pull a plug wire out, you will need a spark plug socket with a rubber boot (usually a 5/8th spark plug socket, and a socket extention that is 6-8 inches.
unscrew each plug and pull it out, the plug hsoudl reamin stuck in the rubber boot of the plug socket so that you can pull it up and out of the spark plug recess.
take the new plug and lube it with a bit of anti seize compound, and carefully thread it into the hole being very carefull not to crosstrhead it. tighten them to 12-15 ft/lbs
reatatch the spark plug wire and repaet for each cylinder.
when all cylinders are done, replace whatever you took off the car.
If you have the 90hp single cam model, i coudl not speculate where the spark plugs are located, but it may be similer.