Koodos Nexus S i9020A.

I took ICS update a few days ago and phone was very buggy... not to mention no data. I wanted Gingerbread back... Looked in this forum and found a post how to unlock and recover to gingerbread. Followed dirrections and got phone unlocked and before restoring to gingerbread, I took a backup. Then did the gingerbread restore. The phone booted fine (with the now unlocked symbol at bottom). A voila in gingerbread... But no service (no bars with a x). Phone funtions fine other than not being able to call, text, or use 3g. After futher searching I found that there's diffrent versions of Nexus S software. And didnt put the i9020a file on it.... so im assuming thats why its not working. I went back into CWM and tryed to restore my backup I made... I get MD5 Mismatch... I also wanted to be sure it wasnt my SIM card so i put my girlfriends SIM card in and same thing no service..PLEASE HELP... I know im a NOOB to the fullest.. but I really dont have the money to buy a new phone. Thanks in advance for anyone willing to give me some help.

Bruce