you will have a GREAT time. don't worry about it. i did London to Paris this year, total of 314 miles over 4 days and it was the first big ride i'd done. The first day i crapped myself looking at the hills (i seriously would have cried but didn't want to show my weakness!) but i did it and i had a great time. here are my tips.
1. it's always more miles per day than the organisers say. when they say it's 60 miles today, get it into your head its going to be 67. the last two miles of the day are hardest, so if you think you are doing 60, you'll be dieing from 58 and it will be more like 65, but if you have it in your head its 67, you'll feel relief when it's only 65.
2. if it's a novice ride, the hills should be no worse than 10% for a mile (that is one that rises one metre in 10 metres distance). find one in your area and train on it. hills are always easier when you are climbing them with someone else. if you're not used to them, keep seated, relax the top half of your body and use your legs (granny gear if necessary) to get up them. try not to stand up unless it's a last resort. you will find it more tiring if you stand. if you don't make it up the ones near you, don't worry, like i said, when you're with a group it seems a lot easier.
3. get a she-wee.. i'm definitely getting one for next year.
4. look at the route and find out what is the most mileage is on any one day. before you go, try and train yourself to be able to complete this amount of miles on one day, and go out the following day to do a 20 or 30 miler. sounds hard, but the more fit you are the more you will enjoy it. the hardest part of these long rides is that you don't get time to recover, which is why you need to be able to do a significant amount of miles on 2 consecutive days. the third day was the hardest for me, but the fourth, being so close to your goal, all the aches and pains just disappear.
5. make sure you stretch out morning and evening, before and after each ride. very important!
6. sudocrem! assos! vaseline! the works!!!!! take it all and put some in a pot to take on route with you. (see also point 9 below). sudocrem works best, it sticks around longer than assos.
7. be prepared to lose your dignity... p!ssing behind bushes etc (often more desirable than continental toilets!)... this is why i'm getting a shewee next year... not for the bushes... for the loos!!!! they were horrible!
8. two bottles of fluids, one with energy drink, one with water. carry energy powders with you in plastic bags for refills on route.
9. proper chamois in the shorts, not foam padding! don't worry if you look a bit "padded out" in the nether regions, i did and i wish i hadn't been so vain! ha ha (see point 6 above)
10. don't forget your camera. take pictures of each other riding (send someone on ahead to take them), and every start, water/lunch stop, and finish each day. at the end bang them all in a photo album in time order and it makes a great story book. they will probably have an official photographer, but we found our own photo's were better.
think that's it. o yea, if you can, organise a meal the night before for people to meet up. it's a great way to get to break the ice with strangers and i met most of the people i rode with on our pre-ride meal, and it really bonded us.
pm me if you want to know anything else. i'm still buzzing from my trip and happy to go on and on and on and on ..... (as you can probably tell)