Not sure if this is the right forum A structural engineer took a look at my basement and told me where to relocate my support posts to make larger rooms. He mentioned to build a concrete pad 3ft X 3ft for the post. However in digging the hole this new pad would hit the old pad. Should I underpin the pad?

Can someone please tell me the best way to install a replacement window in the basement. I have The builder specials there now. These are the single pane glass inside of a metal frame. I am told i need to take the frame out by some and others to just frame inside the metal frame with 1 bys pressure treated wood. The opening inside the metal frame is 31 1/4 by 16 1/2. The stock windows are 31 by 15 for a hopper or 32 by 15 for the slider from home depot/lowes. The window measurements are 31 3/4 by 15 slider and 30 3/4 by 15 hopper. I would rather the slider window which if i cut the outside edges of the vynyl i can probably snugly fit inside the metal frame. What is the best method and most economical? I am told the right way would be to remove the metal frame and frame out in PT wood. Others have said that the metal frame is mortatred in the poured foundation wall and is a real pain in the a$$ to remove. Please help. I want to finish this basement asap. Thanks.