If you have never programmed anything, then I am afraid that Oolite may not be the first project you want to dive in, at least not before you have acquired some familarity with coding and programming principles.
My suggestiom would be to buy a beginner's C programming book and read it carefully and thoroughly, at the same time writing programs yourself as much as possible. Start with simple things, text input/output stuff like a small text adventure. Then, when you have the basics in hand, start with simple 2D graphics and set target projects, like breakout or tetris. Write programs as much as you can and move to bigger projects once your current ones are completed. When you can understand C, it could be possible to move to Objective-C. Ojc-C is not difficult if you have previous experience with programming.
All this is by no means simple, by no means easy and it will take you a few years of dedicated effort before you can approach a project like Oolite, which contains more than 500,000 lines of code. I apologize if this sounds discouraging, but this is how it is. Trying to dive into the Oolite source without any prior programming experience will only result in frustration and waste of time. If you are as motivated as I think you are, you must understand that the process will be long and difficult, but should not give up.
A simple Google search for Obj-C tutorials brings up many results. I still believe that the book approach will be the best, but in case you want to see what you are getting yourself into, try having a look at this example:
http://cocoadevcentral.com/d/learn_objectivec/ . This is a Mac-based tutorial, but the principles should be the same for Linux. Another tutorial that is more GNUstep oriented (consider GNUstep to be a standard library of methods and classes for Objective-C under Linux/Windows) is
http://gnustep.made-it.com/GSPT/xml/Tutorial_en.html. There is plenty of material to study there, but in any case I would not recommend starting with them before you have the basics under your belt.
An excellent general resource about Obj-C is
http://developer.apple.com/library/mac/ ... C/ObjC.pdf. Worth downloading.