Breaking a mesh into pieces for use in Unity3D?

Hi, I have been trouble importing my mesh (made with MakeHuman) into Unity3D. You see, I exported it as a .fbx, which works, but when I import a character mesh, I can’t view them do to the mesh having more than 65000 triangles (whatever that means). So, I looked online only to discover that I have to break my mesh up into pieces, export them as .fbx, and import them back into Unity. However, I have no idea how to break the mesh into pieces, then putting them back together. Any help with this?