This is my first attempt at modeling by reference images.
Now that I blocked out my model what should I do next?
How to I add detail without breaking anything?
Any links to tutorials or just more info would be greatly appreciated.
First off… good job I’m impressed for a first serious model. If you want to add more detail you can either a model it in (won’t be easy for a beginner), b sculpt it in. If you sculpt you wont be able to render easily without baking a normal map to a lower poly version Link: http://www.blendercookie.com/2010/08/30/retopology-and-normal/ , your other option is to leave it as is and just do a detailed texture. I’d suggest next just making a good UV map and playing around with sculpt a little. If you choose the sculpt option you dont have to retopo… just make a copy of your current model and sculpt on that
erm… forget what oeslian just said about the sculpting… only use that for organic modeling… if you want to add more detain just start adding some more edge loops (ctrl + R) and extruding and scaling and rotating… just keep trying 
dont worry about breaking it… just save a backup incase u mess evreything up…
http://www.blendercookie.com/2009/12/05/modeling-a-porsche-911-gt3-rs-part-01/ that is a good tutorial series on modeling a car… it might help to watch that… if not then have a look around that website… theres lots of useful tutorials
Thanks for all the advice!