When a hard drive dies, you lose EVERYTHING. Passwords, bookmarks, games, apps, documents, music, the entire operating system....
It's not a good thing.
The clicking could be part of normal operation. It is a mechanical part, so there will be noise. However, if you are just noticing it now, that's something to be concerned about. Normal laptop hard drives are relatively quiet so you would have to listen carefully to hear a properly functioning one.
While this is by no means a precise test, it is a good enough one to tell you if you should panic yet:
Put your ear to the hard drive as you boot your mac. Listen to the sounds it is making. If you can make a beat out of it, you have a problem. That means the hard drive failed to read something, so it is retrying until it succeeds. If the sound is sporadic and there is no pattern to it, it is unlikely the drive is bad.
All macs have a backup function called time machine. some people have other methods they like better, but for your purposes, that one is fine. You need an external hard drive of some sort to move the data onto. It doesn't matter what brand or type as long is it has enough space to fit everything in it.
Your macbook has a hard drive. Hard drives are terrible in laptops because laptops get moved around, and hard drives do not like being shaken while spinning their tiny parts in a tight space at very high speeds. They are delicate. They are slow. However, they are cheap to replace and hold lots of data.
An SSD is better suited for a laptop. It is more expensive, and doesn't hold as much data, but there are no moving parts to break, they are lighter, better on battery, and FAR FASTER.
If you have the cash, think of this as an excuse to get an SSD. If you can't afford an SSD, mac computers seem to respond well to Seagate's hybrid drives (SSHD.) Those are like a combination of an SSD and hard drive. They aren't as fast as a regular SSD, but they are definitely faster than a standard hard drive.
Once your hard drive is replaced (it's not difficult. look it up on ifixit.com), you will have a computer with no operating system. It will not boot at all. You will need to install one. Newer macs are able to automatically go online and download their OS automatically. I don't know if a 2010 MBP can do that though. you should be able to create a USB flash drive installer though if you download your OS from the app store.
After installing the OS, your mac will ask you if you want to restore from a previous state. This is where time machine is handy. Connect your external hard drive to the mac and tell it to restore from there. This part may take a while, but that's normal. It has a lot of data to move over so just give it time.
After this is finished, your computer will look and behave as if nothing was wrong. you will be right back where you were.
While you are already in there replacing a drive, if you don't have much ram, this is a good time to upgrade that. An SSD can make your mac faster, but there is no substitute for a good ram upgrade.
