I dont have a tried and tested plan as such but this winter i joined the forces and had physical education lessons 4 or 5 times a week, this consisted of circuits working upperbody and cardio lessons. i gained a little bit of muscle on my upper body and strenghthed my abs alot. This was from doing just core strengthning exercises such as sit ups, crunches and planks, and upperbody exercises like press ups and lifts etc, that was for bout 9 weeks or so, after the 9 weeks i was able to get out on my bike. im pretty good at going up hills being quite light but struggle into the wind and sprinting. After doing all this exercise i can tell im carrying more weight on the hills (although some of that may be me over indulging haha) but my sprinting ability and ability into the wind has improved, i feel more comfortable and in control of the bike, i personaly feel its from my upperbody being stronger especialy my abs and back.
As for diet it depends on what your aiming to achieve and the amount you get out on the bike and your personal goals. Try to cut alot of the c**p out your diet such as fast foods and sugary drinks etc etc. Also an idea may be to take whey protein to increase protein intake and help muscles grow and recover. Try to eat as much fresh food as possible and possibly supliment with vitamin tablets and omega 3 tablets to keep the joints supple and heart healthy. Also i read a study somewhere that says omega 3 can help weight loss by making the body colestral drop or something

dont know the truth behind it but cant be all bad!
sorry my answer is so long winded, i just have to much time on my hands haha