You asked "I've wondered if the THA will help resolve my bursitis, but after reading your blog I just wonder if it will..." The short term answer is probably - the inflammation will be improved once the damaged joint is replaced.
But, bursitis is a quirky thing - several years after hip replacement, mine flared again. At that time, the ortho gave an injection, AND told me the only "fix" was to keep the muscles strong through use and exercise. He showed me specific stretches to do, my pain management PT gave me strengthening exercises, and I keep moving all day long, no matter how I feel. If I sit too much, especially in the recliner or on a sofa, EVERYTHING hurts.
So your idea to get to a gym is a good one - but I suggest a visit first with a rehabilitation therapist (get a referral from the pain clinic) who can start you on a gradual stretching and strengthening program.
Then comes the hard part - you have to do it every day, whether at home or the gym, no matter how you feel - other wise it doesn't work. If you cannot get up and down from the floor, ask for exercises you can do while standing, with a chair or counter nearby for balance. Also, many stretches can be done on a firm bed. I do at least 5-10 minutes of stretches every morning before I get up, working on loosening arms, legs, back, neck, and hands.
Sue