as i recall (i made the repair over a year ago) i unscrewed/removed the threaded part from the broken plastic nut, being careful not to let the nut fall into the core support. then i added a nut, of the appropriate size, to the threaded part. then i took a small piece of scrap metal and drilled a hole in the center of it. then i inserted the threaded part through the piece of metal and screwed it back into the broken plastic nut, screwing it in to the proper adjustment position. i don't recall if i held the plastic nut with needle nose pliers, or just kept tension on it by pulling it down while screwing the threaded piece back into it, but that seems reasonable. once i had the hood bumper where i wanted it i tightened the nut i had added against the piece of metal sandwiching the bumper against the core support. the repair took me about 10 mins and i was quite pleased with how well it worked.
this repair was done on my daughter's Mountaineer and she doesn't live with me anymore. i'm visiting her next weekend, if i think of it i'll take a photo of the repair if you'd like.