I'm not sure what you mean by "plug between the step and the wall outlet". Photos would help.
First, I'm not sure that what I.am writing is not entirely true. However, it's not unusual for a plug not to use all the slots. You can probably find another plug at TandTrepair.com or Central Michigan Sewing supplies if you believe it's broken. If you do not have a manual, you can get one
here. Just enter your machine number and download a free manual. it should give you lots of information about your machine.
Second, I would not invest any money to speak of, in a Touch and Sew, except a 600, 603 or some 626s. Those that came later have plastic gears. They shred when they get old. They are expensive to have replaced and difficult for the "shade tree mechanic" to do.
My 758 is still working, but it has always been stored in the house in air conditioning and has been used lightly, as I bought it new. I love the touch and sews, but several machines donated to me for my kids quilting class have disintegrated when used a few days. The kids love them, as they are easy to use and have a low speed. Still, they are not worth fixing unless you have a particular fondness for them or some sentimental attachment.
bkay