Can i delete cydia and reinstall using limera1n?

[inflacoarch]

I have an iphone 4 on 4.01 but my cydia has been running slow to the point where i don't use it because loading changes takes about 4-5 minutes.
I have wanted to update to 4.1 as my friend has it, because it runs fast as hell but when i try updating to the official 4.1 firmware it says something about my device not being allowed to?
Is there anyway to uninstall cydia and reinstall it using something else without restoring?

Thanks in advance!

[i.Annie]

You need SHSHs to restore to anything below 4.2.1. The new Cydia provided by Redsn0w is quick. Check for SHSHs with TinyUmbrella first to see if you have 4.1 saved. If you do, then upgrading and rejb will be easy.