"you know, you should really have a professional do this"
I was watching a current affairs program a couple of days ago, on which they were testing the competence of so-called 'professionals'. In this test, they removed a vital part from a fridge, and replaced it with a defective part. Not only could few of these 'professionals' fix the problem, one couldn't even reassembe the fridge he'd disassembled, and ended up cutting off the power cord, leaving the fridge in worse condition than when he started.
Sadly, this applies to computer techs as well, one need only read
this article to realise that. There have been many times i've received computers to repair, that have already been looked at by other 'professionals'. In many cases, these 'professionals' have turned a simple fix into an enormous problem. I've had customers who have paid up to $600, when the original problem still hasn't been resolved.
By far the worst case, though, was when one of these 'professionals' was called to repair a simple printer problem (the driver hadn't been installed), for someone who later became a client of mine. This should have been fixed in 10 minutes, but, after two hours, he decided to format the computer (without asking the customer). When this (not surprisingly) failed to fix the problem, he charged the customer $120, and left. I was called several days later to fix up his mess, but while the driver installation was straight forward, she had lost considerable important data due to the format.
My point is, that just because someone claims to be a professional, doesn't mean they'll do a good job.
(The numerous quotes complaining about their parents not allowing them to mess with their PC)
My view on this topic is that if you've paid for the PC, then you can do what you want with it. If your parents have paid for it, don't assume you have an automatic right to fiddle with the components. You may know what you're doing, but you can damage something. We see enough people asking for help on a failed build in these forums every day to prove that! While I think that building a PC is a fantastic experience, and something I would encourage everyone who has the interest to try (within reason), I wouldn't expect a parent to fund it, unless they're willing to take a risk. At least if a professional messes up the build, you won't be paying for it

.