Let's start with the technical questions:
-You check the oil with the bike straight up /NOT on the sidestand/. Fill with oil to the upper mark.
- Yes, there is an oil filter. It is under the 3angle cover on the clutch cover. Unscrew the 3  5mm alen head bolts ant the filter will pop out.
- Before You think abiut rejetting You have to install the new exhaust, because the jetting will depend on the intake and exhaust.
-there is not a factory in-line filter, but it is an excellent idea to put one. Also if You have some time, remove the petkock and drain all the gas to make sure thewre is no rust and water in the tank.
About the parts -somebody else will help.