I think that would work. There are only a limited number of shank types on machines -- primarily high shank, low shank, slanted, and Bernina. Most machines are low shank. The dealer should be able to match up the shank on the walking foot with the shank you bring in. Also be sure you know the brand and model of your machine.

Here's a website that shows the basic shank types:
http://www.clotilde.com/pages/which_foot.html

They mention snap-on feet. These are usually snapped on to a low shank ankle. This makes the feet less expensive. However, for a walking foot, you would remove the ankle in order to screw on the walking foot, so the walking foot needs to have a shank that matches your machine's ankle.

Generic walking feet do not always work as well on a machine as the walking foot made specifically for the machine. It depends a lot on the machine and on the quality of the generic foot.