Kristine, I have had 6 fuzzies undergo right adrenal surgery - small
females, large males, youngest was 11 months old, the oldest 7+ years
old.  Two were bilateral surgeries, one was a right only, left intact,
and two were second surgeries within a year of an initial left adrenal
removal.  Luckily, all were successful - all survived the surgery, with
varied recovery times, and all went on to lead quality lives for periods
ranging from 14 months to five years after the surgery.  Two passed from
Addisonian crises (same litter, sisters) and the rest from other causes
(lymphoma, insulinoma, old age).
 
The big however ... I was very lucky to have an excellent very ferret
savvy vet, who is an excellent surgeon.  And I paid for extra tests
(venogram) to see if colateral circulation had already been established.
And I was just plain lucky, period.  I would do it again if necessary,
but the biggest concerns I experienced was the threat of the Addisonian
crisis (a system crash from the lack of necessary adrenal hormones,
precipitated by unusual stress - infection, loss of a companion, etc.
and of course the cost can be much higher.
 
So, good luck - it can be very successful - or not.  You have to weigh
the odds.  I have two who could not have the surgery, and they are on
lupron.
[Posted in FML issue 4714]