Exchange it for what? Or, do you mean simply replace it? Just remove a battery cable to kill the power, then remove the starter push rod and battery cable. Then remove the 3 bolts holding the starter in place and wiggle it around and out. It's a tight fit, but it will come out.
When you remove the Bendix bolt on the rear of the starter shaft, then you can remove the drive head and key, then slide the rest of the drive off. Reverse this to install the new drive, but make sure the tabs are good on the lock washers, or better yet, use new locking tab washers and make sure the tab is tight against the flat side of the hex bolt, so it doesn't come loose down the road. The helix should only have a light coat of very light oil. 3 in 1 oil or ATF should work.