fixing mySQL replication (large DB)
Since you have a functioning Slave, you can rebuild the bad Slave in two different methods
For these examples

MAS : Master:
SL1 : Slave (Good one)
SL2 : Slave (Bad one)

METHOD #1
This method requires that you stop using the good Slave for the duration of the recovery

STEP 01 : On SL2, Run STOP SLAVE;
STEP 02 : On SL1, Run STOP SLAVE;
STEP 03 : On SL1, Run SHOW SLAVE STATUS\G
STEP 04 : Record Read_Master_Log_File and Exec_Master_Log_Pos From STEP 03
STEP 05 : mysqldump data from SL1 to a SQL text file
STEP 06 : Load mysqldump into SL2
STEP 07 : ON SL2, CHANGE MASTER TO master_log_file='(Read_Master_Log_File From STEP 03)',master_log_pos=(Exec_Master_Log_Pos From STEP 03)
STEP 08 : On SL2, Run START SLAVE;
STEP 09 : On SL2, Run SHOW SLAVE STATUS\G and Look at Seconds_Behind_Master
STEP 10 : Repeat STEP 09 until Seconds_Behind_Master is 0

After this, you can use SL1 and SL2 for reads
METHOD #2
This method requires that you shutdown mysqld on SL1 and SL2

STEP 01 : On SL1, Run STOP SLAVE;
STEP 02 : On SL2, Run STOP SLAVE;
STEP 03 : On SL1, Run SHOW SLAVE STATUS\G
STEP 04 : On SL1, Run net stop mysql
STEP 05 : On SL2, Run net stop mysql
STEP 06 : Copy entire datadir of SL1 over to SL2. Make sure you copy master.info file because it contains replication coordinates needed of SL2 to continue replication on startup. Make sure you copied the relay logs as well.
STEP 07 : On SL1, Run net start mysql
STEP 08 : On SL2, Run net start mysql

CAVEAT
If every table is InnoDB, MAS does not need to be shutdown at all. SL1 just needs a stable place to stop replication before copying to SL2.
Give it a Try !!!
UPDATE 2014-03-14 15:51 EDT
If you are planning to use the Master (since you are moving the Master to another Data Center), here is some advice.

STEP 01 : Stop application writes to MAS
STEP 02 : On MAS, run RESET MASTER; (Deletes all binary logs)
STEP 03 : On MAS, net stop mysql
STEP 04 : Copy the MAS server's datadir to the Slave's datadir
STEP 05 : On the new MAS, net start mysql (DO not have any application write to MAS yet)
STEP 06 : ON the New MAS, SHOW MASTER STATUS;
STEP 07 : On the Slave, net start mysql
STEP 08 : On the Slave, run CHANGE MASTER TO master_log_file='binlog from STEP 06',master_log_pos=(Position from STEP 06);
STEP 09 : On the Slave, run START SLAVE;
STEP 10 : Start application writes to MAS

No need to copy binlogs doing it like this. All a Slave cares about is the latest binlog.