Upgrade RAID 1 pair of drives

I have a PowerEdge 2600 server, tag # B1WFC21. It is configured with RAID 1 and has 6 drives so that means 3 pair of mirrored drives. It currently has 36gb drives and I need more space to store Ghost images. Would it be possible to replace one pair with the 146gb drives (Kit # 340-7915)? In order to do this would I have to backup the data currently on the smaller drives and then restore it to the larger drives after replacing them in the RAID array?

Thanks,
Lisa