Hey
paddy,
Congratulations on taking your first steps toward your LL journey. The "scared" part is a given, of course. I think only a deranged masochist looks forward to having his legs broken.
I recovered a lot quicker than some of the twenty-to-thirty somethings that I rehabilitated with in the "cruciate club" after I had my my ruptured anterior cruciate ligament repaired aged 47yrs old. Us older folks know what recovery from surgery is... I've done it quite a few times
I don't want to dampen your confidence, but just to give you some input from a fellow "geezer". I had always healed from injuries pretty easily too. My own ACL repair was a breeze for me as well. The difficulties I've had recovering from LL were well beyond anything I could have imagined. Non-union aside, the stretching of my soft tissues have permanently changed how they feel, it seems. Strength is coming back gradually, but I haven't had a day in which my legs were not sore since 2013. It's not a constant, all-day thing...but walking too long, standing too long, and most strangely, even
sitting too long makes me want to lie down and stretch all my leg and lower back muscles.
If you're doing external-only, at least you won't have the damage to your knees that I have had. But whatever you do, make sure you work on your core strength (particularly in the lumbar area) while bed-ridden and wheelchair-bound. The amount of pain and fatigue that hits you when you get back on your feet is tremendous...and I can't help but suspect that it's intensified in us older folks.
Basically what I'm getting at is that you shouldn't look at it as preparing for a single "surgery". You should be preparing yourself for a severe, slowly-developing
trauma to your body. And your plan to limit to a conservative 5cm is a good idea, IMHO. I only lengthened as much as I did because there was never going to be a chance in Hell I could/would go back for femurs.
Anyway best of luck to you. Keep us posted on your progress.