It is always a good idea to introduce the dog and cat while the dog is very young, but as long as the cat does not run away when introduced they should do fine. Maine Coon cats are usually very confident animals and much less likely to run than some of the other breeds.
How should you introduce the Dalmatian and the cat? That is hard to say because it depends on their individual personalities. If the dog is calm and obedient, you can allow him to come into your apartment when your cat is on your lap. If the dog is more rambunctious, he might need to be put in a crate before introduced to the cat.
If your cat is nervous, and likely to bite you, a slow introduction (where the dog is locked up and the cat is free) is a good idea.
You mentioned that you and your cat are moving in with the Dalmatian, but I definitely recommend that you let the two of them get together for the first time on the cat´s turf. After they have met and are able to get along you can take the cat to the dogs territory. NOT before that.