I thought I'd share my adventures of swapping my 160GB disk for a 340GB disk in my MacBook (Black one, bought Summer 2007).
I have been running this 160GB disk since I got the laptop, and since TimeMachine (Apples built in backup system) became available I've been using an external 2.5" 250GB USB disk for the TimeMachine backup. The reason for the 2.5" is quite simple, it's small, and it doesn't require an external power source. This means I can easily do backups wherever I want them.
To upgrade I bought a new SATA 340GB disk (Western Digital Black). I opted for a 7,200rpm one as I'm mostly using my laptop plugged in, so a decline in battery life isn't that critical. Then I also bought a new external backup disk. My choice fell upon the Buffalo 500GB one. I'm pretty pleased with it, it's black and shiny, pretty much similar to my old WD backup disk.
To get started with the disk swap I watched a YouTube video about it. As it turns out, Apple's hardware is, as it has always been, lovely (and we only buy these machines because they're "shiny" - right!!!). The procedure is, simplified, remove the battery. Unscrew the shiny L-shaped guard by undoing (not unscrewing) the three small phillips head screws. Carefully remove the L-shaped bracket. The disk is hidden at the short end - you'll see a white plastic tab, unfold it and pull the disk assembly out. Use a Torx T8 (I carefully used a Torx T7) tool to unscrew the four bolts that hold the "caddy" on the disk. Swap disks, reverse procedure to assemble. That's the hardware done.
Then you stick your Snow Leopard (or whatever MacOS you're using on the old disk and the backup disk) into your CD/DVD drive. Also plug in the TimeMachine USB disk. Boot the machine. It should now boot up to the Mac OS installer. At the installer choose the option for restoring your machine from a TimeMachine backup. You can now click forward in the wizard interface until you get to the spot where you select the disk to restore to. In my case, my disk was either unformatted or, formatted with the file system of a more commonly used operating system. Fret not, dear upgrader. Simply go to the "Utilities" menu and select "Disk Utility". Locate your new "blank" disk, and on the "Partition" "tab", select Options and choose "GUID Partition Table". Proceed and wipe the new disk and format it with the new filesystem. When done, exit "Disk Utility" and return to the Installer/Restorer. In my case the newly formatted disk was already found, so all I had to do was to select the steaming fresh disk and click forward until the restore proceeded.
The actual restore too about 4 hours or so.
The next part is to move your existing backups to the new backup drive. This is, simplified, done by "just dragging the 'Backups.backupdb' folder from the old disk to the new disk". However, there's a few things you need to do, such as turning the automatic backups off. See this Apple Knowledgebase article for full details: Mac 101: Time Machine. The information is under the "Mac OS X v10.6: How to transfer your backups from your current hard drive to a new hard drive" sub-heading.
BUT! There had to be one, hadn't there?! The Apple KB article mentions that "This may take some time to complete". In my case, "some time" meant 24 hours. I'm not kidding you. You have been warned! Now, there's a speck of good news; Firstly you don't have to do this on your own machine. You can use any Mac (or any other machine that can read/write that OS - I'm guessing) to copy the folder over. Secondly, I assume that using a command line option would be better, such as plain old cp (copy) or rsync (remote synchronisation). If I'd do this again, I'd use my girlfriends Mac and I'd use rsync to do it. That way I could interrupt the copying if needed.
Once you've got your old backkup on the new backup disk, it's time to reactivate your automatic TimeMachine backups and obviously to choose the new disk as backup target. And then you need to make a new fresh backup of your system. This might take some while as the file modification times have changed etc. It took about 2-4 hours for me - I don't know exactly as I don't know when it finished. :) Also, Spotlight will want to index your new backup disk too (process named mds), so expect your laptops fans to whirr away whilst this is happening.
So, not totally painless, but a lot less pain than I expected. If the backup copying would have been faster I think it would have been pretty much totally painless. There's a few caveats, but all in all, quite a straight forward process.
If you wonder about the faster disk? Did it make any difference? Yes, it has, but it could also be due to that the machine, now, has got "unlimited" swap capacity. (160GB+ compared to 1-4GB before). The machine feels a bit nippier and I'm very pleased with it. Battery life has decreased quite a bit, but the only time I've ran it off battery power, I wasn't very kind to the CPU with a lot of software running, so that was definitely contributing to the short battery life. Either way, very pleased. :)