Upgrade from 3.16 to v5.02

[btd]

In production, we are currently on Vault Server version 3.16 (SG3658) on Windows 2003 Server SP2 x64 OS. We purchased 30 licenses from you.
We have set up a test environment (same OS) with 3.16 on it, just like production.
We want to "test" the upgrade to v5.02. I see where we can download a trail version. This is not what we want. We want to upgrade to v5.02 without restrictions.
Is this possible?
If so, how should I proceed in getting my test environment upgraded to V5.02 so we can test.

Also what are the new features in V5.02?

Thanks

btd

[btd]

Since we are on maintenance, is the upgrade free of charge?