It can be replaced without removing the floor.
Do have to drill the spots at the floor to the x-member.
Then the spots for the x-member to the front frame rails.
Then the spots for the x-member to the rockers. The x-member has tabs that go between the floor pan and the rockers. At that point you need to cut the pan there and lift it to get to those tabs on top of the rockers. Once the new X-member is in then lay and weld those cut areas back down.
Not real easy but very doable.