The motor on the #8 is similar to other motors you may be familiar with in that the parts are the same, just configured a bit differently. Standard cleaning and repair techniques are used.
The Hobby Horse wheel press with the proper cups will come in very handy to press the new wheels on properly; however, unless you plan on doing many wheel replacements, the cost is high for just one job. Perhaps a nearby Lionel dealer will do the job for you for a reasonable fee?
Here are a couple of videos to get you started
Larry
