I ran it last year, it's 4 and a half laps (i think) round rockingham race track which is an oval, it was very windy and wet, also a tad boring as there is nothing to look at, but very flat , I wouldn't do it again, good luck if you do it
I also have really bad knees (41yo) i had to stop cycling they are that bad and couldnt even walk far my knees hurt so much, ive tried averything from insoles to loads of different knne straps/tapes etc.
Then i heard about barefoot/minimal running and havnt looked back, i started with new balance mt110 and ran my first 10k in them, then moved on to the new balance mt00 which are also brilliant and now im changing slowly to vibram fivefingers.
When my nb mt110's needed changing i went to Sweatshop and had all the test done and they recommended a certain pair of "normal" trainers, a good thing they do is let you try them for a few weeks and you can exchange for a different pair which i did as they killed my knees!
Keep going, i stated last feb using a couch to 10k app and it worked, really hard to start with but keep going, now im running about 15 miles a week and my new years resolution is to run a 10k every month