I could not find any guide for removing the starter from a 1.6L 1999 Nissan Sentra, Incl. Haynes and Chiltons. Remove the air box top, filter, MAF and duct. Remove the three screw/bolts from the bottom of the air box, and set the box aside. Disconnect the battery terminals and follow the negative cable to the bolt thru the bellhousing and into the starter. You just found the starter. Remove the bolt from the starter but leave it in the hole through the bell housing. Just to the right is an electrical connector, disconnect it from this side. It is the control line to the starter soleniod, which is mounted to the starter. Lift the car and put jack stands under the front on both sides (Remember to set the parking brake and chock the wheels). Remove the passenger side front tire and plastic shield allowing you to see along the back of the engine to the tranny. Loosen the support bar from the intake manifold to the frame below/behind the oil filter. You will now be able to get a socket with extension to the starter bolt. You can now see the starter and solenoid. Remove the positive battery cable from the solenoid stud. Remove the remaining bolt holding the starter in place. By wiggling the starter it can be removed without removing the oil filter, although that might make it easier. You can not remove this starter from above, you must raise the car and work from below. I removed the battery from the car while working under the hood, it only took about a minute and gave me alot more space. I did check the starter before disconnecting the battery by shorting accross the starter solenoid. If the starter had turned over the engine I would not have continued to remove it.
No need to raise the vehicle. the starter is located on top of the transmission just under the air intake pipe. It is not located on the engine as most are.