First you will need shsh blobs to upgrade/restore.
Open cydia and look at the top of the page to see what firmware versions are listed there.
In Cydia, the following is listed:
SHSH: iOS 3.1., 4.0, 4.0.1, 4.0.2, 4.1, 4.2.1+, 4.3, 4.3.3, 4.3.5
but when I run TinyUmbrella v.5.00.12, It lists the following:
4.0, 4.1, 4.3.5, 5.0b1, 5.0b2, 5.0b3, 5.0b4, 5.0b5, 5.0b6
Which one is accurate? And what upgrade paths are available to me at this time?