Did you have a look at the TestBed project? It's full of examples of the things the engine can do. As a matter of fact I suggest you start by modifying a TestBed item and only move to XNA graphics when you are really comfortable with the physics. XNA is
not easy at all, even though it might seem so at first glance. Add to that a physics engine that is by definition really complicated and this can get easily overwhelming even if you are an expert in .NET.
In the testbed you get for free a game loop, input management and quite useful automatic DebugDrawing with camera matrices set up for you to perfectly match the physics with no need of thinking about conversions and scale. Making a real game, of course,
is much more difficult but this really has little to do with the engine. The samples are a step in that direction with some useful stuff but they are by no means complete and are not a real game engine just a prototype.
Anyways Farseer is a port of Box2D so everything that is Box2D related can be useful with minimum effort if you are good at reading c-like code . Box2D has a pretty decent manual that is linked in the documentation section. There are a few sites with great
tutorials for Box2D and its ports (Flash, Java ecc):
For example Emanuele's site (flash) has 130 tutorials for Box2D related stuff including how to make an Angry Birds and Angry Birds Space clone (the original does indeed use Box2D itself). He's also writing a book. Iforce2D covers some interesting advanced
topics and frequently asked questions. He also has an interactive editor (RUBE) to build and test scenes that has a free version and soon a Pro version that look very promising.
http://gamedev.stackexchange.com/ have lots of answers even for Farseer not to mention Box2D.
Even though Farseer has almost no documentation don't give up! There is a huge number of resources that can help. The problems will come later when you try to do real complicated physics... :)