I guess we know why he didnt find the amp...LOL another way of knowing if you have an amp is one plug (there two total, plus antenna) from the radio will be square this is the radio's output to your amp, if you have two rectagular plugs (one black, one gray) you have a regular HU without an external amp.
The doors are a pain, actually it is quite easy, but doing it without damaging the plastic is difficult since Ford decided to use the softest plastic they could find. just take your time and be patient otherwise you will really aggrivated and end up with some messed up panels.
