1996 Mercury Grand Marquis needs a new power steering unit on scale of 1 to 5 being very difficult is this an easy job or job?

While not overly complex, it involves working under the car, dealing with potentially messy power steering fluid, and requires some mechanical aptitude. There are several bolts and connections to disconnect, and some maneuvering might be needed depending on your tools and access. It's not a 5-minute job, but a reasonably experienced DIYer should be able to handle it.