How easy to replace core support bushings.

[THE "10" SILVERADO]

Pulled the lower front valence off of my truck to access some of the upper bumper bolts, and while I was at it I noticed that the core support bushings are easily accessible. I have some poly bushings left over from my cab mount set so how easy is it to change the bushings? Unlike the cab I don't think I can just unbolt them and jack up the core support so what other options are there? Trying not to have to pull the core support...

Thanks