How cheap and easy it is going to be depends on what you want to do?
I wouldn't say fibreglassing is rocket science but it's not that easy either.
What are you aiming for? Have you any idea at all what you would like it to look like?
You also need to think what Subs you are going to use cause you will have to calculate the amount of space behing the sub for it to work properly. You can't just make a fibreglass build and throw a sub in it does need to be thought out very carefully.