I had a 4-5-6-7 fusion in 1985 . I was not an avid cyclist at that time and was 34 years old. I had bone removed from my hip for the fusion.
My recovery time was two months . The primary therapy was swimming. I returned to my prior job as a welder in a heavy manufacturing plant.
My surgeon estimated I lost about thirty percent strength in my left arm and there is definitely permanent nerve damage. Lost some range of motion turning head to left.
Have very mild pain in arm every day.
it will occasionally flare up but aleve takes care of it. I also use fish oil in large guanities for a few days to help with inflammation.I do not routinely take any pain meds of any kind.
I took up serious cycling in 2004 and have done a lot of long distance. I have completed RAGBRAI six times.
I hope yours is at least half as bad as mine . You should be able to return to full duty.
I crashed in 2006 ,did a face plant that hurt my neck and I wass off bike for two months.
PT brought me back.
Get an experienced surgeon who specializes in this procedure.
Goog luck you should be fine . But expect to lose a little but still have more than enough.