Can I install a solid state drive?

Any drive you purchase must be (or be able to step down to ) SATA (1.5Gb/s). Since most SATA drives can only drop back one rev at most you can use a SATA II drive (3Gb/s).

Any SATA III (6Gb/s) drive that claims to work on your machine should be warrantied by the vendor in writing so that you do not incur any restock or return fees.

Since you can only get partial use from Snow Leopard you might want to stop at 10.5.8 for complete functionality.

If this answer is acceptable please remember to return and mark it.