Hi frrok,
I am sorry to hear that you are having issues. I am sure you already have this link, but I'll post it anyways.
QuickPwn OSX Guide | iPhone News, Help and Guides This guide by far is one of the easiest to follow that I have come across. I follow his guide for the PC, and yes there are some differences from the guide and what exactly shows up during the process, but it is still a very good guide.
As for why Cydia is not showing up, I have read that if you had Categories installed, it could screw it up. I came across these instructions to fix it.
If cydia is not working:
1: Restore phone from iTunes.
2: Jailbreak your phone.
3: Install boss prefs from Cydia, and unhide the wanted icons.
The only problem I see with that is if you can't find Cydia because it is hidden, then how are you expected to install boss prefs to unhide it.
Of course I am assuming that Cydia did get installed it is just not visible. This link might be more promising,
How To Restore Your 2.1 Backup | Sleepers.net. You might be interested in step 2b.
This link has the same infomation,
HowardForums: Your Mobile Phone Community & Resource - Cydia Installed, but not showing up on springboard
Hope this helps.
-Cruce