lmc makes very good sheetmetal. and no offence. but if your asking what is involved in doing something like floors, you may not wanna tackle this job.
but anyway, first thing to do is gut your interior. seats, carpet, padding, ect. lay the new metal ontop of the old metal and trace around it. cut about a 1/2 inch in from this line. now refit the piece, and do your final triming. then what i like to do is mark the floor braces from the underside to the floors, pull the floor out, punch holes through the floor to land on the braces and punch around the perimeter of the floor. then lay the piece in for the last time. put zip screws in the holes you drilled to suck the floor tight to the brace. then remove one at a time and plug weld the holes shut. then seam seal around the patch, and your good to go.
hope this can be of some help to ya
dave