First: Where exactly do you ad brake fluid? And Second: everytime I
step on the brakes I hear this high pitched whine/buzzing along with a
flashing light that looks like a fan inside a rectangle with a fluid
symbol above the fan. Both the noise and the flashing light stop a few
seconds after letting off the brakes. What could that high pitched
buzzing sound be? (hint: the sound is similar to what a car antenna
retracting sounds like) Please anybody help!

Add brake fluid at the reservoir, on the drivers side, attached to the
firewall.

Sounds like you have 2 problems. 1- your brake pads are dead. That
light is a brake pad indicator that you are hitting the sensor to the
rotor. Replace pads all around for best fix.
2, your ABS is probably flipping out, thats what is sounds like when
activated. I would recommend the following. Go under the hood and find
the abs control (drivers side, mounted over the wheel well, it has
brake lines coming out of it.) disconnect the wiring harness from the
abs. Drive truck and see if the noise is still there (Im willing to
bet its not), if this is the case, your wheel sensors are probably
toast which is causing your ABS to act up. If the noise is still there,
then I have no idea...

This of course after you have made sure your fluid is at the correct
level and visually inspected the brakes for problems.

This really isnt technical at all, just get in there and get familiar
with what is under there... and if you decide to sell it cheap... well-
let me know, Im always looking for a good RRC.