it runs! also help with rust

finally,
me and my dad replaced a broken fuel hose that connected to the fuel pump. it wasnt an easy job since gas was leaking... we managed to do it without losing any limbs or body parts. the hose was so old, when i pressed the accelerator the hose ripped completely in half. thats why we had to replace it. now to make sure everything is ok, we are going to replace the other fuel hose since it is also old just in case. i do need a little help on deciding to replace my exhaust system. i cant tell if it is surface rust or worse. i havnt found any holes but still... when i rub my finger slightly on the rust, it comes off on my finger and particles fall. i will have pictures up as soon as i can, possibly tonight. also i have a question... what is an engine block? is it just like the bottom frame part or what?