Remove the battery ground. Now you can go below and remove the wires to the Denso starter. There will be a fat wire from the battery or, if your car uses one, an external solenoid. There will also be one smaller wire, either a ring lug on a stud or a spade lug, from the ignition key. Older vehicles with points-and-distributor ignition may have a third wire to the coil, bypassing the ballast resistor. Don't get them confused.
Now get a socket and ratchet and probably an extension, and remove the bolts holding the starter to the block. You may also need to remove a heat shield, brace or sheet-metal cover to get everything loose. Don't drop the starter onto your head as the last bolt comes out; it's as heavy as a bowling ball.
Don't get out from under the car just yet. Mark one tooth on the ring gear with some spray paint or even chalk, and inspect every single one of the 140 to 160 teeth by turning the engine over with a big screwdriver for one full revolution. Seriously damaged teeth will require replacement of the flex plate or flywheel, which commences with removing the transmission from the vehicle. Fear of the necessity of this should motivate you to fix a balky-but-still-barely-working starter before it damages the teeth. Labor to remove the transmission and replace the flex plate or flywheel will be 6 to 8 hours, more if you have four-wheel drive. Add in the cost of parts and a ring gear replacement could easily reach a thousand dollars or more.
Take your old starter motor to the auto parts store and exchange it. Don't be surprised if the new starter bears only a faint resemblance to the older one. The industry has been transitioning to smaller, lighter gear-reduction starters that use a higher-speed motor coupled to a planetary gearset to spin your engine faster while using less current. The new starter will have grease already in places where it's needed, so no further lubrication is necessary or desirable.
Replacement of the new starter is straightforward, at least if your vehicle doesn't require shimming the new starter. Snug up the mounting bolts, reinstall any braces, covers or heat shields, and hook up the wiring. All you need to do now is reconnect the battery ground, take the vehicle off the stands and start 'er up.
