Craftsman Planer Blade Change

A friend has loaned me his Craftsman planer on a long term basis. I'm trying to plane some 12" wide maple panels, but the planer is bogging down, even on the lightest cuts. I thought I'd change the blades, but I don't know the process for this machine (model 351.23378). Firend says he might get around to looking for the manual some time.
Sears wants $10 for the manual, but I was hoping that someone here might be able to spell out the process for me. Shoot, I'm not even sure which way to turn the nuts clamping the blades in place.
Thanks, Ed Bailen
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