Software raid partitions

[Tanuck]

I have a server with 2 x 1TB drives. When I purchased the server they install centos 6 with software raid 1. With partition table for the mirrored drives looking like such:

/boot 500MB
swap 1GB
/ rest of free space

Without having to reinstall and request a custom a partition table, I'd like to shrink the / partition so I can increase the swap space to ~30GB.

I have vague knowledge in this area but I wanna be sure.

Can anyone instruct me how to go about this?

Thanks beforehand