Whenever I brake, it feels like Im landing a space shuttle. Lots of bumpiness and shaking. Is it the break pads or something worse?

Also, whenever I accelerate quickly, especially on the freeway, I smell this
sulphuric kind of burning smell. It only happens when I accelerate quickly. How concerned should I be?

How much would these things cost if i took them to a mechanic?

 

my brother had the shaking when breaking in his pathfinder i think he needed a sway bar replaced
my brother and i go to this mechanic that gets junk yard parts and then puts them in extremely cheaply i had an inspection break pads and oil change for like
$140