My mother-in-law (age 90) had to undergo a kidney biopsy about two months ago. She was already in the hospital due to complications from what was later diagnosed as micro-polyangitis, a form of vasculitis that impacts the kidneys, lungs or both. In her case, it was the kidneys. At any rate, her biopsy was done with a radiologist guiding the nephrologist by way of an ultrasound. I was allowed in the room (masked, gowned and gloved) so I could comfort her as she also has dementia. It appears to be a relatively quick and also relatively painless procedure. The only thing they recommended once back in her room was to minimize movement as much as possible for the ensuing 24 hours.
I agree with straydog. If you're not already in a hospital, this procedure would be done on an outpatient basis and probably take a total of perhaps two to three hours, including prep and recovery time.