i have a 503a, which is fairly similar to the 401. it's the only machine i've ever had, never needed any repair and i bought it at an estate sale in 1989. since then i've made a zillion kids' clothes and at least a dozen quilts and a few craft-type projects. i'd try oiling and greasing it yourself and asking here if that doesn't do the trick. there's a wealth of advice here and i imagine people could guide you in anything else that might be wrong if oiling/greasing doesn't work.
if it were me, i'd probably restore your mom's machine just for sentimental value.