SSD Question (Using it as "Storage")

Are you putting both drives in 1 PC? You only need 1 copy of win 7, on the boot volume - is that what you meant by "do I need to install Windows 7 for it to support trim?" What other OS are you considering?

Any used SSD would need to be Secure Erased before used again, to regain the factory performance settings.

After that, install Windows 7 to it, let Windows 7 create the partitions (very important!) and do not use any other utility to create partitions or format.

That should get you an aligned partition with TRIM enabled.

The SATA controller mode should be set to AHCI in the system BIOS.