I run the K&N oil filter part number KN-153 on my 99 750ss and synthetic oil; the recomended viscosity is 10W-40, and this is a good all around viscosity .
The oil capacity is about 3 liters but you should always keep an eye on the sightglass and the oil level markings. Not really sure about the convertion to quarts, sorry.
The starter is a bit harder than it should be. First remove the wiring cable, then you need to remove the lefthand crankcase cover to gain access to the starter mounting bolts, there are 3 of them and for one of them you have to align the bolt with one of the holes of the idle gear. Keep in mind that the manual recomends to install a new starter gasket when re-installing the starter.
For the best prices on the starter try your luck on ebay.