Crucial M4 256 GB or Samsung 840 (non-PRO) 256 GB SSDs can be had for 150 USD, 128 GB can be had for 80 to 100 USD.
As for tools, a simple Philips #00 screwdriver should do the trick.
MacBook, MacBook Pro: Replacing the Hard Disk Drive, transferring data to the new HDD
the guide includes:
- 0. Identify your MacBook or MacBook Pro
- 1. Getting a new HDD
- 2. Guides to replace the internal HDD with a newer one
- 3. Transferring data from the old HDD to the new HDD
- 4. Using the optical disk drive (ODD) slot for placing an SSD or HDD inside the MB/P (OPTIBAY)