Root Experienced Users - Plz Help - Remove Superuser.apk or Put Stock Back - ROGERS

[inningsdefeat500]

I got my replacement phone and need to return the original

My issue is that I unrooted and the Superuser app is still there on my phone and I tried to follow the instructions

su
rm -r /system/app/Superuser.apk
rm -r /system/xbin/busybox
rm -r /system/bin/su

I downloaded Terminal app but I type "su" it says invalid command

I also have downloaded the Stock Rogers ROM

Can someone please please either tell me how to

1) Remove Superuser app form the Phone
OR ( better yet in your opinion )
2) Put the stock back ( but have no clue how to do this )

I have tried googling, searching but there is no simple answer and since this will be returned, I ave limited time

So any kind soul can help a fellow Captivator