The Seagate Momentus hybrid is 9.5mm tall and a SATA drive, so it should work in your Mac even if it is a pre-unibody 15". Since it is from 2007, it is a pre-unibody.
Look at both ifixit and powerbook medic for instructions. I don't know if Apple would install it for you, since they generally only want to install drives like the ones that originally shipped with the machine. However, if you decide you don't want to do it yourself, you could look for an AASP in your area, who could also do the cloning operation.
Is your old drive in good shape, or is it failing? If it is failing, you would be better off to install all the software fresh from discs and update it and then migrate your data. Here is a guide for doing that:
http://discussions.apple.com/thread.jspa?threadID=435350&tstart=0
You can find good enclosures at OWC. Check their clearance/garage sale page for specials. Be sure to get a SATA enclosure and not an EIDE one. Especially good are the Mercury on the Go Firewire enclosures. I have several of these and they're great!
I'm about to do the same next week with my 2007 machine, since the hard drive started going south a week after my Applecare expired.
Good luck!