Studies show that your pre-operative status has a lot to say about your post-operative progress. Your level of physical fitness before a hip or knee replacement is often able to predict your recovery after surgery.
The fact that you were active and a leader of a hiking group is very much in your favor. After six months it is reasonable to expect to resume many of your former activities. But if you had some hip muscle weakness before the hip replacement (and it's likely you did), then you may need a more specific rehab program for this particular activity.
We can suggest two things for you: 1) See a physical therapist for an updated exam and exercise program. Let him or her know your goals, so the program can prepare you for the level of activity you are interested in. 2) Use a walking stick or pole.
Research shows that trekking poles reduce the load, increase stability, and decrease soreness associated with hiking. In fact, a simple walking stick may even decrease your risk for injury and allow you to maintain your active lifestyle for much longer.