Yes if you have had problems with weights - then go easy on that side. WEight lifting can imply really full on - as in the sport - that may be way too much intensity. Progressive resistance training may be good but the intensity of ex shouldn't be too high especially to start off with. One thing to think about is just introducing one component at a time and letting your body get used to it. So I would definitely start with the aerobic component first. Much better to gradually introduce things and gradually increase exercise intensity and thereby avoid stopping because you have made yourself sore.
And it might be good to get some advice from a PT who looks at muscle imbalance issues so that you strengthen up the right muscles
Re pain medications: It sounds to me as if you need some ongoing support with this side, particularly as you aren't finding something that really helps. I am not really qualified to advise you on medications - really is more a physician thing. There are a number of options re: chronic pain modulation so it is worth exploring further. But make sure you are dealing with a physician who really knows about dealing with chronic pain.
One thing though - I would be cautious of taking opiates with a chronic pain problem - that group of drugs may be great in the short term but they can cause all sorts of problems with your nervous system over time - drug dependency being just one of them.