I used a small thin screwdriver to pry the split rubber feet out of the grills. Then I applied a small amount of high temp. sealant to each rubber foot before inserting into the hole in the Grill. I used a paper towel to remove any excess sealant. The sealant insures that the foot will not fall out. The job is done and I would rate it as very easy.
The sealant I used was DOWSIL RTV Sealant 732 which is recommended for High temperatures
to 350F.