Re: Laptop won't switch on
Those commercila prices are for the time taken to do the job, the knowledge they have to do it, and the risk they take that something goes wrong doing the job, as well as their overheads in maintaining a business. The actual component is a small part of the repair bill.
As for guides, if you have found nothing on google, you are looking to see how it comes apart yourself. Some cases clip together, with or without screws, some have clip on covers that expose case screws (I once spent an hour taking all the screws out of a laptop to change a CD drive - turned out that there was a clip on cover that gave access to it - total time, 10 minutes - but thats experience - and what you pay for commercially!)
So you need to carry out a careful visual inspection to see how the case migfht fit together. Screws are often hidden under labels, or in foot mouldings.