Welcome to FF14!

The previous poster pretty much said everything that needs to be said but I'll throw in my things.

1) The server I'm on is Cactuar which are very friendly and helpful. Cactuar can be overcrowded at times and some places can take a while to fully load but usually that's limited to Mor Dhona.

2) The beauty of CNJ/WHM is that it doesn't really need much from other classes but as mentioned, you will love Swiftcast when you need to revive other players.

I'd also like to mention that the early dungeons will be the first real test of your CNJ skills but these dungeons leave a lot of room for error and a quick mention that you are new to healing to the group when you enter will make your experience even better.

The dungeons themselves have a good learning curve so once you have the hang of one dungeon, you can proceed to the next with confidence. Keep in mind that every group is different. Just keep an eye on that MP.