iPad 3.2.2 to 4.2.1

[iPadRTR]

New here and new to ipads but so far I'm really liking it. I bought my iPad used and it came with 3.2.2 installed but I would like to upgrade to 4.2.1 and then jailbreak, solely for the purpose of getting ibluever to tether w my blackberry. So here's my predicament- now that 4.3 is out I can't use the auto update and when I try to select the 4.2.1 ipsw file to restore within iTunes I get a 3914 error after iTunes tries to verify with their server. I've been looking at going to 4.3 and downgrading but I don't have any "blobs" from the older version which i believe is a requirement. Am I screwed or is there something Im missing or can do? Thanks in advance for the help