l have and 07 sportster what all is involved in changing the oil in the engine or do l change the transmission oil alsodoes the engine have a lower oil drain plug or do you just drain the oil tank?

u should change both the fluid in the primary case as well as the motor oil u will need 4 quarts of 20-50 motor oil & 1 quart of primary chain & trans fluid & one oil filter ,
1)after warming up the motor l like to take mine out for about a 10 to 15 minute ride to heat up all the fluids
2)put a small drain pan under the bike
note make sure it can hold 4 quarts with room to spare !
3)remove plug from trans case & hose clamp on plug located under the motor in between the frame rails just in front of the smog canister
4)remove old oil filter
5)install drain plugs & new oil filter make sure to wet the rubber seal on the filter with oil before installing
6)remove small inspection cover located on the side of the trans case
7)add one quart primary chain & trans fluid then replace cover
8) add 3 quarts 20-50 oil in the oil tank
9)start bike & check for leaks at filter & drain plugs
10) shut off motor & check oil level in oil tank & top off if needed

excellent how to instructions at xlforum.net or sportster.org