You'll probably have to install the fixed version of 3.56 via the recovery console.
As for the speed of the drive, I'm using an eSATA 3.5" desktop drive which is connected to my PS3 with a homemade cable (that way I can use a much larger and cheaper HDD than is available in 2.5"). Anyway, the desktop drive should be much quicker, but I honestly see no difference on my PS3.
Also, a word of advice. Before purchasing a specific hard drive, check and see what other people who have installed it in their PS3 have to say about it. A good site to check is Newegg.com (good place to buy too). Search the feedback for PS3 and make sure people are saying it works good. Some drives can be a bit flaky and give errors or cause the XMB to stutter and pause.