Data security when sending Macbook for repair

I purchased a 17" Macbook Pro a few months ago. It's my first Mac, and I love it, but unfortunately it decided not to turn on a few days ago. I went through all of the recommended troubleshooting steps, and it's still dead, so I've decided to hand it in to Best Buy to be repaired (I have an accidental damage plan). Here's my problem... there is sensitive data on the computer, which, because of my profession, I am required by law to keep private. Given that I don't exactly trust Geek Squad (or anyone for that matter) not to go poking around on my computer, I'm wondering if there is some way to protect this data before it's serviced. I'd rather not wipe the drive clean if it can be avoided. So far I've considered swapping out the hard drive with a different one and just replacing my old one when I get it back, although I've never done that before, so I'm not quite sure how practical it would be. By the way, I do have a startup password on the machine, but I'm assuming that's probably not truly secure. Thanks in advance for any advice!

Without being able to start the machine you don't have much of a choice. If the data on that hard drive is of a nature that others should not have access to it, you probably should remove the drive and replace it with another.

Have you been making backups? Time Machine? If you have a good backup on an external drive, it will make the swap a lot easier.

Some info you may not be aware of concerning Best Buy and Apple computers: Unless the repair is a simple one, the Geek Squad is going to send it on to an Apple repair center to be worked on. I would suggest if you have an Apple store close by, to make an appointment with them and bring it in to them to repair instead. You have a one year warranty with Apple. If you purchased an extended warranty with Best Buy, that will cover the machine after the one year expires.

Regards.

I would certainly take that to an Apple store ANY DAY over Worst Buy.

I knew somebody who worked for Geek Squad - standard procedure was to go through all of the client's stuff.