3GS 3.1.2 Oldbootrom re-jailbreak and unlock

[periohead]

hello, i bought a 3GS 16GB iOS 3.1.2 with baseband 05.11.07 old bootrom previously jailbroken with blackra1n and unlocked (backsn0w). Cydia icon appears but there's no other application installed and all the contacts and messages were also removed from iphone (i don't know if the user erased all contents and settings). so problem is that cydia crashes everytime i try to open it and it will not install using blackra1n on the iphone. when i use iphone browser the iphone is not recognized as jailbroken and no ssh is installed on the iphone so i'm not being able to get to the file system and i don't have any SHSH firmware backup. For now i can use my current sim card but i'm using the phone as not jailbreaked and i have some issues (youtube, cydia and push notifications not working....)
so is there any way to rejailbreak the iphone without loosing the unlock and how? can i use redsn0w 0.9.2 and then ultrasn0w to unlock after the blackra1n or i have to restore my iphone to factory settings using itunes before? will i preserve my current baseband? thank you

[iYeow]

Go download tiny umbrella, plug your iphone in and click save shsh.
If you see 4.1 shsh blob in TU, then start tss server.
Update your itunes to the latest.
Download Snowbreeze 2.0.2 or 2.1 and create a custom firmware of 4.1
Run redsn0w 0.9.6rc8, browse to stock 4.1 ipsw.
Check only the dfu box.
Once dfu is done, run itunes : shift + restore to cfw of 4.1
Update cydia and install Ultrasn0w to unlock.

[periohead]

No 4.1 saved shsh in tinyumbrella...only 4.2.1!

[i.Annie]

You can do the same steps above just with a 4.2.1 ipsw. But you'll need PwnageTool. If you don't have a Mac, you can ask someone to send you a custom 4.2.1 ipsw without the iPad baseband update since you don't need it.

All you'll do is follow iYeow's steps and substitute wherever he said 4.1 with 4.2.1 starting at "Run Redsn0w" (of course after you find your custom firmware online).

[periohead]

thanks...well i got access to a mac now coz i dont wanna risk downloading custom firmwares from the internet...
should i use pwnagetool 4.1.2 or 4.1.3 and should i mark activate button or redsn0w will activate it later?
do i have to patch PwnageTool 4.1.2 With PwnageTool Bundle (i dunno what they are)
do i use redsn0w or the newest greenpoison to jailbreak?