Retribution 101 -- courtesy of WoW.com This is a very helpful, up to date guide on how to get the most out of being ret Paladin.
If you switch to Prot, you will have significantly reduced time in dungeon queues, but you will have to be more prepared; the group's success or failure will depend on you much much more than it ever has before. Not only will you need to be prepared in terms of talents / gear / glyphs, you will need to be familiar with (a) basic tanking strategies, such as Line-of-sight pulling (not so much anymore, but it's an example), how to control adds, and how to use your cooldowns to keep the most important members of your party alive (usually your healer -- BoP is a godsend) and (b) the instance. You will need to know which parts you can pull large swaths of easy mobs in, and which you need to do 2 or 3 at a time. You need to know boss strategies and be able to explain them to other people. It will also help if you are patient, and able to motivate those with you to follow your lead, rather than run ahead and aggro things that you then must pull off of them. Being a good leader goes hand-in-hand with being a good tank, and being a good tank will indubitably improve your leadership skills, if you are not already confident in that regard.
I don't think WoW.com has a Prot 101 guide up yet, so the best resource I can send you to for what to do in preparation for tanking is the
Elitest Jerks guide. It may be a tad bit out of date, but contains much good material.
Good luck! (We always need more good tanks, so I encourage you to make the change)