dang man.. thats gonna need some work! my 20g sat in a tractor shed for 10 years and looked better than that 
for the back, it looks like the only option is sanding. paint strippers could be an option, but i wouldnt want those chemicals near my aquarium.

for the back, it looks like the only option is sanding. paint strippers could be an option, but i wouldnt want those chemicals near my aquarium.