Jeremy,
I could answer part of your question, about the radio.
Your radio/tape has what is called a "battery-backup" wire in the back
of the unit. It is usually marked somehow (depends on the brand) BB, or
aux, or something that shows it is different than the main power lead.
It is usually a small red or yellow wire. This lead supplies power to
the radio when ignition is off, keeping station settings, time, last
volume settings, etc. What I've seen with other radios installed by
novices is this wire is connected to the main power lead, instead of
running a separate lead from the fusebox.
Hence, forgets stations! You need to add a wire from an "always on"
source to this lead on your radio, or take your van into an auto radio
installation shop and have them do it.
Hope this helps!
Doug
'90 GL