I messed around with the code and looked into the renderEngine class fine, I believe that func_98187_b has been replaced with bindTexture. The game no longer crashes when it renders the texture, however, the texture comes up as white with black stripes, like the missing texture thing. I think that I'm using the wrong string import for bindTexture, but I'm not sure. Currently using
Minecraft.getMinecraft().renderEngine.bindTexture("/mps/models/ArmCannonTexture.png");