If it works, no reason to call a tech. No reason to replace it either, provided you don't hate the way it looks/functions. Even if you don't want to self clean it, I would still use the fume free, self-clean safe version of Easy-Off.

It seems to work. I did use Easy Off for a few minutes today and that seemed to get off most of the baked on areas. There are still some stubborn places that aren't coming clean, but I can live with that. The enamel is definitely worn on the bottom and one of the sides. There is a place on the side where it is gone completely and rusted, but only about a 1/2" diameter. There is also a quarter sized section under the bottom burner in the back that is not coming up. It is rust colored. Maybe a scorch from a fire?
Just the little bit I played with it, the oven seems to work fine. It preheated to 350 in less than ten minutes.
I would prefer not to replace it right now as the dishwasher does need to be replaced and we can only afford to do one right now!

I think you can keep the oven for a while longer. You have cleaned it, used oven cleaner and ran the temperature up. I don't think running the self clean cycle will do any more to remove residual spots. Any residue is solid and won't come off into food. I wouldn't worry.