There's really no substitute for experience.
I would focus on the blaster and read up on build threads specific to your make of kit. The more research the better prepared you will be.
When you get the kit, resist the urge to tackle something visible like the helmet or chest. Start with something small, like a bicep, it's mostly covered anyways, so if you mess up it won't be as noticeable
Go slow, measure twice, cut once, don't rush and try not to get frustrated. Also, engage your local garrisson, most have members that are willing to help out "shine-jobs" like yourself
Of course, the most important is engage the community here on the forum, we're here to help too.