First time on a "budget airline" - cabin baggage size

don't know when you are flying but if it is in the next month or so check you flights carefully. Ryanair are having major pilot staffing problems and are cancelling round 50 flights a day fro various airports so please check and double check your flight will be available

It can be easy to stay within the size requirements, but realize that the weight is what gets people, you need to be under 10 kilo, or about 22 lbs. This is difficult for a longer trip. I would just go in and Pay to check a bag. The total cost will still be much cheaper than other options and you will have no worries.

Oh no Unclegus! I am flying Ryanair because I was advised by a Delta pilot friend to avoid Alitalia who code shares with Delta. I could have gone all the way to Palermo with sky miles. :( We are flying in November. Now I am nervous.

A 10kg baggage weight limit can be met if you don’t haul the kitchen sink.

Oh no Unclegus! I am flying Ryanair because I was advised by a Delta
pilot friend to avoid Alitalia who code shares with Delta. I could
have gone all the way to Palermo with sky miles. :( We are flying in
November. Now I am nervous.

Ryanair is cancelling 40-50 flights per day for the next 6 weeks because they scheduled pilot vacations at the same time and thus don't have the pilot crew. You should be fine as your flight is in November and the reports state that flights are being cancelled until the end of October.

https://www.cnbc.com/2017/09/21/ryanair-cancels-2000-flights-ceo-admits-issue-was-badly-handled.html

List of cancelled flights

How Ryanair will compensate including putting passengers on competitor airlines.

http://www.independent.co.uk/travel/news-and-advice/ryanair-cancelled-flights-pilot-shortage-pay-for-rival-airlines-civil-aviation-authority-a7961221.html

Thanks Continental. I did find the list of cancelled flights earlier today. They say that an email will be sent if a flight is canceled. So far we have dodged the bullet.

Also not really concerned about weight of carryon bag. I will be checking one bag. I just don't want to be denied because it is 3/4 inch too thick.

Most airlines have sizing boxes at every gate these days. If you can get your bag in and out of the sizer (i.e., if it is soft-sided and not fully packed), you should be OK. If not, you could have to check it at a very high price.