SATA I and SATA II are cross-compatible. The connections are the same. SATA II has a burst rate of 3GBps vs 1.5GBps with SATA I. In the end, this is just raising a typically untouched ceiling. ATA drives typically sustain around 40MB/s or so.
OEM hard drives will include nothing with the drive. Retail versions typically include the cables and diagnostic and formatting tools (the software isn't required to use the drive and can be acquired for free from the manufacturer).