I have had both hips done so if you have any questions at all, feel free to ask me. I assume you will have physical therapy after your surgery. The therapist will probably see you a day or two after your surgery to get you up and walking down the hospital hallways. Then you will probably have more physical therapy for a month or so. They will help you learn to walk with a walker, go up and down steps safely, then walk with a cane in the correct way and drill into you the movement restrictions you'll have for the first 90 days or so. You will do all kinds of hip flexor and leg strengthening exercises and pretty soon you will find that you are forgetting your cane all over the place and you will know you are getting back to normal. It sounds like you will do well, considering that you are active and going to the gym so much. You may breeze through the whole process and you will be very glad that you had it done. It will be wonderful to walk without pain!
No one told me this next item the first time around so I want to tell you in case you haven't heard this. You may not be able to move your leg much at all at first. For example, I couldn't lift my foot off the floor or bed at all. I couldn't move my leg sideways at all. The muscles and nerves can be traumatized by the surgery and have to relearn some things. My physical therapist said that the connection between the brain and the muscle fibers has to be re-activated. So you have to do what you can, get your husband or friend or therapist to help you do the exercises and you will get it all back soon.
I wouldn't worry about losing weight right now. Just concentrate on getting mobile and strong. You may lose weight anyway, though, just because of the side effects of surgery. I lost weight the first time because I didn't feel well for a couple of weeks and didn't want to eat. The second time I felt fine and hungry and didn't lose any weight to speak of. Both times I did a lot of water walking and water exercises but you have to wait until the incision has healed up. I had my second hip done last June and am now going to a low impact exercise class 3 times a week. I modify some exercises as I think best. For example, I don't do the grapevine, I just step sideways. I have been doing personal training for a little over a month too. The first couple of weeks were a lot like the physical therapy I did last summer. My doctor has told me to do pretty much whatever I want but not to walk 3 miles a day to lose weight because it would wear the hip out earlier than necessary. I stay away from the treadmill but do the elliptical. I do low impact, not high impact. I don't jump or run or ski but don't miss them. I never did much of those things anyway.