Hi Jay,
In fact there is no option of aux in the system, only a tape and radio options. I saw that they sell online a convertor to connect directly to the radio to make an aux and USB plugs, but it does not fit the plug I have (see the pics).
FM radio transmitter has too much interference for my opinion, at this point I think I will just get a new radio.. thought I could solve it with an adapter but looks like it's not going to work..
Thanks anyway for the help