Nice work for a first timer
A warning about trying to use foam/fiberglass resin - most resins will simply eat the foam away. You'll need a polyester resin to seal the foam before fiberglass work.
Suggestions:
Create a framework/skeleton for the basic structure and leave the back side open - then stretch/staple fleece (found at any fabric store) over the skeleton. Once stretched/stapled apply several layers of fiberglass resin to the fleece and let harden. Once the fleece is hard you can apply the fiberglass matt to the INSIDE (hence leave the back of the piece open) and be left with a much smoother surface to finish prep. For finish work you can start with SMALL ammounts of bondo over the fleece to fix the larger flaws. For the final finish you can use a sprayable high-build primer/filler. This is basically a thin/sprayable bondo that sprays very smooth and is MUCH easier to sand than bondo/fiberglass matt.
This site provides excellent tutorials and basic project examples:
http://web.njit.edu/~cas1383/proj/main/
Heres a couple of advanced tutorials:
http://www.jlaudio.com/tutorials/mera/MERA_2002.pdf
http://www.jlaudio.com/tutorials/mera/MERA_2003.pdf
Good luck with your project(s)!!