Ok, there's some good advice here.... speaking personally from ALOT of experience:
1) First and foremost, always get an MRI (and X-rays) to find out exactly what's causing the problem...otherwise, you'll be spinning your wheels. Different injuries require different courses of action.
2) Avoid any barbell bench presses... use dumbbells as a substitute. You shouldn't be sacrificing much in the way of gains/results.
3) Do stretches for 5-10 minutes several times a day. There is debate as to whether or not you should do considerable stretching right before a workout, but some light stretching is a good idea, or at least 10-15 minutes on a bike to get the blood flowing.
You can do a search on-line for some good shoulder, neck, & upper back stretches. Very important to keep the muscles in these areas limber otherwise you're opening yourself up to injury.
4) While experiencing pain, ice for 10 minutes several times a day. Very good to keep inflammation down.
5) SEE A CHIROPRACTOR - This has made a HUGE HUGE difference for me. People will disagree, but for me, there's no question that seeing a chiro regularly has greatly reduced my shoulder/neck pain and prevented it from happening. Neither a physical therapist nor an orthopedic surgeon could do what my chiro did.
6) Low-dose deca will help throughout a cycle; expressly for joint support, keep the dosage low (200mg/wk or less). Anything more than that and you're actually negating the joint benefits. Also remember that when you stop the deca, the pain will always inevitably come back.
7) For "maintenance", it's a good idea to take OTC stuff such as glucosamine / chondroitin, EFA's, and maybe even gelatin. You'll have to take then for months or longer to notice any effects, but it could be worth it.
Final notes: Forget the cortisone shots, you'll become dependent on them to the point where they no longer work in relieving pain, plus they weaken the joints and tissues. Use surgery as a very last resort. Do the stretches religiously, ice, use smarter/proper techniques at the gym, and if you're in alot of pain, skip the gym for a few days or longer if necessary. It's a hard concept to swallow but would you rather skip a week or a few months later down the road?
Good luck!