Firstly - WELL DONE 
I ran two marathons last year and I am running two this year - one being M/CR marathon
I have ran a maximum of 22 miles in training for each marathon and have been absolutely fine on the day for the previous two and Im sure I will be fine for M/CR. The crowd will push you for the last 4.2 miles anyway.
Im sure you will have a fantastic day and dont set off too fast - keep to your own pace.
M/CR marathon was last held 10 years ago so dont really have any tips!!
Have a fab day and I am sure this will be the 1st of many marathons you enter - it does get addictive!!!!!