Can I rent a car in Dublin or do I have to make the car rental part of my package when booking a trip?
You can rent a car anywhere in the world. If you're talking about the drive/stay coupon packages I think it's just that - - an all-at-once package. I've never done it that way, nor has my wife - - we've both felt it was not the best deal. I'm starting to think we're in the minority with that opinion, but we're sticking to it.
Car rental doesn't have to be part of a package but you WILL want to book it ahead of time. In fact, book as soon as you know your dates. Then keep watching the rental sites to see if better deals come around. You can always cancel your original reservation and rebook. Depending on when you are traveling, you might not find what you want available if you wait till you arrive.
To piggyback on Nancy's reply, advance booking is especially important if you plan to rent an automatic. I booked my car through Auto Europe. It is easy to cancel a reservation through them. I think my actual car came from Budget.
I have done the driving trip through Ireland... It was amazing and having a car gave a lot more freedom and the rental process was very easy. But make sure you get the full 100% insurance coverage! Lots of the roads outside of Dublin are small and cramped! Make sure you are covered internationally by your insurance company at home as well!
There is no need to be covered by your car insurance company at home when you get coverage with your car.
A good piece of advice is to remove any wheel covers on the left side of the car. It is almost certain that you will hit curbs and don't want to have to pay for replacement wheel covers if you lose one.