Difficult....not really. Hardest part, removing all the carefully applied factory caulking.
Everyone has a preference as far as replacements, I used one from Inland RV,
much better quality than the one used by the Factory.
Others prefer the bullet proof options.
You'll probably find that yours is cracked because the person responsible for it's installation couldn't control his screwdriver!
Ours was cracked at every screw hole.
Same with the Fantastic Vent hinges and black tank vent.
I would advise a trip to the AS roof and inspect first-hand.