What I would do is the following
enamal covers-Try some "T" cut to remove the top surface and hopefully remove the staining. If not and the stain has gone too deep, use some very fine wet and dry rub the enamel down removing the top surface. Then "T" cut this to bring up the shine.
If this fails, get the doors ,etc resprayed with enamal. A motor paint shop should do it, or local furniture restorer. If this is a non starter, just get the damaged items replaced, via the spares dept of the range manufacturer.
With the wooden work tops, a tin of wax and some fine wire wool should sort them out.
Hope this help
CATMAN