59 firewall & steps question ?

[wahl4m]

i m getting ready to replace my 59 gmc firewall w/ a new repop one plus the steps w/ the rockers made on them ,has anybody used the repop firewall and steps ? where do i start ? when i drill the spot welds out of firewall will the body try to distortor drop ? also on the steps ,they are all there -some rust through/just need to replace to look nice thanks guys