MSP upgrade from 9.0.0.7 to 9.0.1.5 on Windows Server 2003 R2

We are on a Windows Server 2003 R2 platform and just recently upgraded our test environment to ESP 9.0.1.5. I would like to know how much time would be involved in upgrading to MSP 9.0.1.5 from 9.0.0.7? We have some time constraints so I'm just trying to determine if we should do it now or later in the year when we're not so constrained. How difficult is the process as I'm fairly new to the world of Lawson and never performed an MSP upgrade?