What I did right--though the timing was off--my surgery was a right and wrong thing. Doing it actually improved my situation. But it came with some consequences and modifications. It really threw off my training season. If I had to change it--I would have seen someone sooner....listen to the pain!!!! If it is persistant--speak up and find out what is causing it. Mine was a mensicus tear. No big deal--but what a difference to not have it at all. I didn't know the sensations several months earlier were the result of that--I could have had it taken care of immediately instead of watching my times and skills start to suffer.
If your knee swells get it checked out! (that was the sign that finally made me call the doctor!).
Training--spend the time to train to train--get in shape, tone up, lose weight before training season. When you are training--you cannot diet...you cannot due a serious weight training regimen (mild toning--but not getting chiseled and certainly not getting "built"). The off season is the time to prepare your body for this. Get moving--incorporate a lot of cross training, diet to lose weight if that is your goal. When the season starts--expect to gain, maintain OR lose weight--but not any one of those in particular. Don't expect to gain weight, don't expect to lose weight, don't expect to maintain weight. Expect that any of those things are possible and you will not be bothered if what you wanted to happen doesn't happen.
As John Bingham says--you train so hard for the event--enjoy it when it comes--don't concentrate on getting it over with as soon as possible (i.e--trying to get a "fast" time). "You have 7 hours to finish--what's the rush?" In other words--train to make it within the time limit and enjoy yourself from there. "It's Disney world for pete's sake!"
I broke my own rule--but I'll repeat it--cold baths--ice if tolerated post run. I didn't--I took a hot shower. WHAT WAS I THINKING!!!! Do this after all LONG DAYS. Your body will thank you. With hot showers--your body will HATE you. Mine did! Ouch!
Most importantly--go get John Bingham's book "Marathoning for Mortals". Read it, study it, live it during training. He knows his stuff and he is right. His program will get you to the finish line.
During training--throw in some 5K races just for the race day experience--don't try to win it--use it to plan strategies on how to deal with butterflies--how to get yourself from the start line "slowly" and not "sprinting". Use it to practice "race pace". Practice race courtesy and walk to the right, run to the left.
RACE DAY:
BOOK HOTELS EARLY!
Stay at POFQ and walk to the start! Longer sleep time--get in some indoor plumbing bathroom visits with one last stop at the port o toilet prior to getting into the corral.
Only 1 nights
I will only stay at ONE hotel next time. If I need the nights I will book them all in the same place. I was at Music on Thursday and at CBR for the weekend with my TNT team. I needed the extra night--really should have just added it at CBR.
I will have family go to the start before it starts--park their vehicle. Leave it on with heat if necessary--use a cell phone as an alarm clock and fall asleep until 5:30am -6am. If you have a family member with a camper--bring that puppy to the EPCOT parking lot.

. Carry a cell phone and have your spectators carry one as well. Use the Live results feature if offered. Tell them "don't call me, I'll call you!". Towards the end I got so many calls from my sister from the transportation fiasco that the last call of "where are you" put me over the edge---I had to tell her to stop calling. Don't be afraid--it is very distracting AND it slows you down to keep answering the dumb phone. You will call them.
Stay in a hotel with ELEVATORS or on the first floor. Our team was assigned to CBR--they don't have elevators. I had no idea! I would have requested first floor had I known this. Painful yesterday and this morning--I perfected the teeter climb to get up and down them so that it wouldn't require bending my knees.
Go for it--I'd say the worst that can happen is you get swept. But we had a teammate (TNT) that got swept on Saturday. And for her troubles she was offered the choice of "A" powerade or "A" water and a 2 hour tour of the WDW property while security figured out how that bus could get them back to EPCOT.
If you do get swept--use your cell phone and call your family. We saw a couple of families at the end of the full--the last person came in and their person did not. They had no idea where they were.

.
If you see a runner sitting on the course--this is NOT a good thing--report it to an offical (this happened at the finish--and while most are distracted trying to get to the finish--we tried to get other participants attention to get him assistance and they thought we were cheering them on

I'm sure they didn't know he was there--a spectator jumped the fence and grabbed a cop to get him aid).
Hope that helps!