I need plumbing advice ASAP!?

Go get yourself a snake, any hardware store should have them.

Does the water rise in the tub when you run the sink? That usually happens when tree roots have my main sewer line clogged. I go rent a power snake with a 5/8 cable to clear the roots out, it is hard, dirty work! The fastest way is to call someone like 'Roto Rooter' (about $200), but you won't have to do the job!

try using a thin wire to clear the clog , if that does not work take off the drain control/ access and try from there.. there should be just 2 screws and you'll get better access .