I am wanting to connect an mp3 player (not ipod) to my 03 tacoma's factory head unit. It is a cassette player with cd controls but no cd player. what is the cheapest way for me to hook my mp3 player up to it besides the junk fm transmitters. Also, what model of stereo is in my tacoma? How much can I expect for accessories to get my mp3 player connected?

 

http://www.discountcarstereo.com/detail.aspx?ID=548

Read the compatibility and application notes in the middle of the page!
Looks like you will have to pull out your stereo to see what size connector you have on the back of your stereo.
When connected, you just hit the CD buton twice to switch to your mp3 player