Upgrading my HDD

I would like to change my HDD in my iMac, that you all can read about here on the side.
The 500GB is just not enough, I have been putting the brakes on adding media to it these past few weeks. There is about 190GB left (after cleaning up like 30GB), and I would rather know what I want to do now rather than when applecare is all the way gone in October.
I went onto OWC and clicked through to my 2010 iMac to this page;
Memory up to 32GB for Apple iMac 2010 Models - 21.5" and 27" 2.8HGz to 3.3GHz DDR3 True PC3-10600 at OtherWorldComputing.com
After that I was like, ok, need my brand of the HDD in my iMac. I googled the a couple codes/identifiers underneath.. about this mac>sys.. info..>sys.. report, and one of those searches showed up with a 500GB Seagate HD. So now that I know I have a Seagate under the hood I traveled to this page;
Seagate Barracuda 7200RPM and LP 5900RPM Serial ATA (SATA I / II) Hard Disk Drives (Internal / Bare Drives)
I feel comfortable saying that this is where I need to be. I will probably get the 1TB, or either of the 2TB; considering my back-up arrangement tops out at 1TB currently that decision will lead to another possible purchase if I need to increase my backup ability.
So, do I need to purchase a different 'caddie' or 'holder' for the new HDD? Or is my current one 3.5inch as well? Is there a concern of the new HD working with Lion?

I have watched at least 2 dozen videos of people doing this switch, and I feel safe saying that I could do this. I need to buy the proper tools.

Any input helps, thanks.

The 2010 iMac and 2011 iMac use a proprietary hard drive loaded with special firmware in order to control the temperature sensor on the drive. If it's replaced with any other drive, the fan may go full blast.

Do some searching in our forums and the Apple user forums for more information before attempting to change out the drive.

That's exactly something I figure out on here. Thank you.

Why don't you just add an external drive? I wouldn't mess with the internal drive unless I had to, which in my case I do as it crashed. And 190gb is still plenty of space unless you already have enough stuff to fill it. In that case though you probably already have another drive and don't need to put it on your internal.

@ zacster..
it certainly would be cheaper and easier. the only external i have is my TM back up. i guess i could jget an ext. but then i would be juggling 3 drives right? my HDD, my TM back up and the 3rd yet to be determined drive.

I'd have to go +1 on the external drive reccomendation.

In my experience HDDs are a lot like closets (and pants for that matter); no matter how big you buy you tend to fill it up. Especially when it comes to media (personal photos and such in particular that are irreplaceable) I am beginning to use external drive(s) for these.

Note the plural. I keep 2 drives (one of which goes in my lockbox, or better yet my safe deposit box) the other I work off of. I swap them out periodically to keep them in synch.
I say 2 drives advisedly because I am actually considering splitting my video and photo libraries to their own seperate drives. Not so much because I have filled the external drives but because it makes for easier file management (or at least I think it does) and cleaner workflow.

Ok. So it seems the advice is saying to just go big on an external(s).

One question regarding that. After cloning and copying and what ever, if I decide to boot from any external I am under the impression that needs to be FireWire connected. Correct?

I am thinking about this one, I don't think it has shipped anywhere yet so I will surly wait for reviews.
Iomega Mac 2 TB USB 2.0 Companion External Hard Drive 35130 (Black/Silver):Amazon:Electronics
Thanks