OKay, here is an update:

First of all, thank you for reponses. I knew some of the points
mentioned and was reminded about those. I learned some new
ideas/tricks as well.

The stubborn/partially stripped out screwhead is used to secure the
top Broil heating element to the oven's ceiling. Thus, use of a vise
grip was not immediately possible due to interferance with the bracket
for the element.

I gained access to the Broil heating element's terminals by opening up
the rear cover to the walloven. Although no physical signs of
damage, an ohmmeter check shows infinite resistance (open circuit).

So, I used a hack saw to cut the mounting element near the stubborn
screw, thereby being able to now remove the heating element from the
oven. Left with an L shaped piece of remaining mounting bracket, I
used a pliers to twist and remove another section of the mounting
bracket. Then a vise grip on the screwhead finally enabled removal of
the screw from the walloven.

Unfortunately, the appliance parts distributor, normally open until 12
noontime, was closed, yesterday. I hopefully will find a replacement
element on Monday and get this annoying project completed.

Thanks again for your infos.

de ~ Vince ~
Long Island, NY