The starter has 3 major exterior components; front plate, barrel & rear plate. The 2 bolts that hold the starter on to the bell housing go through all three components & hold it all together.
To remove the starter, unscrew the bolts out of the block & put a nut on one of them. Otherwise, the starter comes apart. Not fatal, but not fun either. (tip # 36 at the link below) Then, loosen the two bolts holding the oil filter canister to the block, (it does not need to be removed) remove the dipstick, and keep the starter close to the block while pushing the front of it down and lifting the back up. Sometimes you have to remove the drain petcock as well.The bendix is behind the flywheel; your job is to get it over the flywheel.
Caution: while the starter is off, resist the temptation to screw with the bendix. If you extend the bendix, and it is not the OEM bendix w/ the big spring, you will have a hard time getting the starter installed.
To install the starter, keep it close to the block while pulling the front of it up and pushing the bendix back into the hole. The bendix has to go behind the flywheel; your job is to get it over the flywheel.
Lastly, while the starter is off, polish the block & all starter mating surfaces w/ sandpaper to insure a good electrical ground. First, clean the mating area between the barrel and rear plate. Then, clean the mating surfaces where the aluminum rear plate meets the bell housing. The starter's ground circuit is not only through the two long bolts but from the barrel to the rear plate & then to the bell housing as well.