get a harness adapter and 2 packs of crimp caps for very easy and fast installation of head unit. Metra or Scosche make the adapter, there is just one model for all 87+ camry/solara which fits all toyotas like this:
http://www.bestbuy.com/site/Scosche+...A02B&cp=1&lp=1
you can get them from crutchfield or best buy.
depending on your current system you may have an amplifier plug for head unit at the back of the deck, but generally there should be an amp bypass plug below it.
you really want to get an amp bypass harness adapter. stock amp sucks,don't try to use it (even with correct adapter for it) as it will work very poorly with new head unit. instead use the new bult-in amp in the head unit