Model DUI401 Run 67? Ser 782898RG51 (best guess)has a rust spot at the
juncture of the white base and circular ring under where the spinning
spray arm is. Is this something repairable or retardable or is
failure imminent? Inquiring minds would like to know. We bought
house 6 months ago and think maybe we've bitten off more than we can
chew. Major expenditures aren't on our shopping list but are viable
if required

The question would be "how old" is the machine? Can you get the service
panel off down on the front and look in with a flashlight to see if
there are any water leaks, etc.??

Stuff like pumps, timers, valves can be serviced/replaced, but that is
about it, IMHO.