I don't normally post on this forum, but I saw your post and wanted to help out. I'm an occupational therapist specializing in hand therapy, and as a student I did some clinical work with musicians with hand injuries. Your experience isn't uncommon, and there are indeed resources for musicians. I don't know where you live, but many major cities have doctors/specialty centers that will treat performing artists- a great resource is the Performing Arts Medicine Association (www.artsmed.org). Also there is a book geared toward musicians, "Playing Less Hurt", that lists resources for musicians. You'll want to find an orthopedic surgeon experienced in performing arts medicine, and, just as importantly, a hand therapy clinic skilled in the treatment of musicians. You'll be going to occupational therapy for 4-8 weeks and likely wearing a splint for part of that time.
Finger joint replacements are not that unusual. The recovery time can be a couple of months, and you will have to take a break from guitar playing for a time. I'm not an expert on outcomes- you'd need to ask a surgeon who has done many- but I think they vary. You have a younger age and I'm assuming relatively good health on your side.
Cortisone shots are short-term solutions and may lead to breakdown of joints and tissues with repeated injections. Again, I'm not an expert so take this all with a grain of salt and ask your doctor. But I hope this helps a bit. Good luck!