Outsource it. Seriously way easier if you just find a local installer and contract it out.
You gotta learn sometime and this sounds like a good job to learn with! if you mess it up it's not much material to reprint and try again. after you have finished it you will start to build your confidence in your abilities!
as for pricing the job, why not price it by the hour with a "not to exceed" clause, so if your hourly rate is $70, and you think it will take no more than 3 hours, quote them:
$70 per hour, not to exceed $210
that way if you are done in 2 hours you bill accordingly, but if you run into trouble, you can call your customer and work something out.