[BNaylor]

I would recommend reviewing a service manual, preferably the GM Alero FSM before starting this type work. You will have to prep the car by removing the respective hub first before you will be able to remove the axle shaft. Before that the ATF must be drained out of the transmission. You will need a special seal puller tool to get the axle shaft seal out and the new seal must be pressed in. Normally a special "J" tool is needed for that too but you may be able to improvise. Also, there is a thrust bearing for each axle shaft. To replace that if it is making the noise then you will need to remove the tranny side cover assembly which is a PITA of a job.

BTW - A company called ATSG makes service manuals specifically for the 4T45E autotransaxle.