Adding 2720 SL Bench Seats

Hi, I am considering purchasing a 2720 SL that I have found for a great price. But, I haven't been looking for the SL, due to the sleeping arrangements. I am wondering if anyone knows how easy it would be to add the small bench seats that fold out into a bed. Or even to add one of the full size beds turning it into a regular 2720.

Thanks

Teressa