The ride and recovery, and knees and things

So we survived the MS Bike Ride.  M did the whole 25 miles - she claims she actually did more like 27 miles due to getting lost with another MS Biker that had trouble following the course.  I only made it less than 3 miles.  I did at least 2.5, but less than 3.  So I guess that makes me a 10%-er.  Kind of fitting in a way.  I am a leftie - like supposedly 10 % of the population.  I am gay - another supposed 10% of the population.  Who knows there is probably lots of other things I am that matches only about 10% of the population. 
Saturday was extremely hot - it was almost 90 at 6:30 when we arrived to register.  Plus the heat index.  The route was all rolling hills, and not gentle ones.  I don't do well with hills.  Especially steep ones.  My knees can't handle it.  So after pedaling what I could and walking the bike up the worst of two really big hills, I was on the side of the road catching my breath.  Wondering the wisdom of even being out here in the heat, when a SAG vehicle came by to ask if I was ok.  I took him up on his offer of a ride back to the start/finish.  He said no shame in calling it quits.  Which I didn't feel any shame.  I got out and I struggled and I did what I could handle.  If I had kept going, I could have gotten myself in a serious mess.  M asked me if I was sure I didn't want to keep going, and I said no.  I did the right thing for me.  I did what I set out to accomplish. I raised over 1175, and I went out and tried.  Next year, we are opting for a "flatter" event.  Flat and gentle hills I can handle.
Other than trying to ride on a day that was way too hot - temp & humidity, I've been enjoying being back on my bike.  I am making an effort to get out and get more exercise and to eat healthier.  I know that if I was to lose some weight it would help with my knees.  Course that too is a catch 22.  If I felt better, I would feel more like exercising, if I lost some weight my knees would feel better, making it easier to exercise to lose the weight to feel better to exercise.  Oh well, it is easy to procrastinate, and find excuses.  It is time to just get busy and "do" and stop waiting for something to magically happen. 
I am trying to decide whether I want to plan to have a knee replacement next year or not.  I want to lose some weight and get physically stronger, and get my knee especially physically stronger before doing that.  Originally my osteo wanted me to wait until I was 52 at least.  Now he seems to think I'm a candidate now, whenever I want to do it he will refer me (he doesn't do that surgery, he does the non-invasive stuff, and surgical alternatives).  So seems to me he is saying it's getting time to do it.  My concern is that I want it to help give me more of my life back.  But what if it doesn't? Not being in pain all the time would be a great thing.  If it gave me the ability to exercise and not constantly evaluate things as to whether or not my knee will allow me to do this or that... those would all be pluses.  On the other hand, I've also read and heard it isn't for people who are looking for some miraculous cure, or that it won't eliminate all the problems, just will help with the pain, that with a replacement you aren't suppose to run or jump (ok, not that I do either now anyway), but I also can't kneel, crouch, etc.  One reason I was always told to wait, and hold off is that the life span on the knees (the plastics) is only 10-15 years, and since you can only replace the knee 2x per knee in a person's lifetime I didn't want to end up not being able to walk at the end of my days.  The other thing I keep thinking is that if I keep putting it off and wait for some magic time frame to arrive, what if I wait too long, and MS strikes and I can't walk anyway.  So, I've decided I just have to determine if it will help me today. if so, then I should explore doing it.  If it won't help me today, then I should wait.