One of the best introductions to the subject is certainly Thurston's Three-dimensional Topology and Geometry, Vol.1 (not to be confused with his much harder lecture notes Three-dimensional Topology and Geometry). It has almost no prerequisits, but leads you right to the statement of the geometrization conjecture of Thurston and some surrounding mathematics.
A more topological view on 3-manifolds is presented in a set of notes by Hatcher: http://www.math.cornell.edu/~hatcher/3M/3Mfds.pdf
For mapping class groups, i.e. groups of homeomorphisms of surfaces, you may have a look at Farb's and Margalit's http://www.math.ethz.ch/~bgabi/Farb%20Magalit%20January%202011%20version.pdf . This is not directly related to the Geometrization Conjecture, but mapping class groups are extremely important both in 2-dimensional and 3-dimensional geometry.
Edit: At some point you have also to learn some differential topology to understand geometric topology. I myself learned differential topology (partly) from the book by Bröcker and Jänich, but this is a little bit terse - there might be better choices. But the nice thing is that Thurston's book does not really presuppose any deeper knowledge in differential topology.
I want also to comment than none of the above sources says anything about the proof of the geometrization conjecture; but I think, it would be unreasonable to try to understand the proof with your current background anyhow.