As I am now an expert on ADHD issues in libraries (self proclaimed) I thought I would share another answer I sent to a reader on the topic. (all personal details removed to protect their anonymity).
Did you know you had ADHD before becoming a librarian? I just started the meds about 3 weeks ago for ADHD. All I have read recently explains my life. I was already struggling w/ depression/anxiety...
...I thought I found my niche here and because of my condition I feel like running away. I really love my job, it's just that continuing problems have finally come to a head. ...I have been a "go-to" person at my library. I have taken on more responsibility than I get paid to do.
...Part of my problem is that my supervisor is more of an administrator than a manager
I guess I started working in libraries before I knew I was ADHD. But I sure suspected I had it before I studied to become a librarian.
There is lots of stuff in your email that sounds familiar to me and not all of it is to do with ADHD. There are plenty of librarians who are stuck in a rut and refusing to look at the amount of good we could be doing in terms of techno changes and the like.
I also find that there are a lot of baby boomer librarians who should be put out to pasture because they can no longer cope with the pace of library innovation or they just don't care any more and they are blocking the way for the gen X librarians (me [and you?]).
So it is worth remembering that there are plenty of mentally stable librarians out there just as frustrated with that sort of crap as you and I are.
As for the diagnosis (and meds)
I found that the official diagnosis and a bit of reading on the topic did more for me than the meds. You probably know from reading my blog, but I don't (always) see ADHD as a problem. Sure it can cause problems (in your case it seems some depression) but that is something which could be treated separately from the ADHD. After all if I read between the lines of your email I think it seems like you have been doing a damn good job in the library up till now.
So knowing what problems are likely because of the ADHD enables you to work towards solving them. Which is to my mind a better option than throwing the baby out with the bath water.
After all if you are the 'go to person' and you accept lots of responsibility then it shows that you haven't been a failure in your pre-medicated days.
My advice (I'm an advice columnist now).
Look at as much stuff as you can on generational theory in the workplace.
think about which of the problems you are facing have more to do with attitude to technology/library management and so on than they have to do with ADHD.
Then learn about your ADHD, trial the meds. Be willing to experiment with the doses (under Doctor's supervision) then decide if there is a benefit from them or if you would rather accept the downside of ADHD because the upsides can be so much fun.