When you start redsn0w, there are 2 options: jailbreak and extras
What trijethero was trying to get to was a rerestore but as stated, it's going to be very hard to guide you through the steps if you have trouble with the simple stuff (I understand that this may be hard for you but these are very simple, there are much more complicated stuff out there and if you have trouble with the simple stuff, the hard stuff will be even harder)
You can always try rejailbreaking with greenpoison v0.4 and see if that brings back your cydia app as installing with the .deb file doesn't work
Are you certain you're downloading the correct .deb file?
http://apt.saurik.com/debs/cydia_1.1.3_iphoneos-arm.deb