three things: Dash kit, wire harness, and antenna adapter. each costs $15.
the dash kit will be a plastic panel that will match teh factory dash, and have a DIN sized hole for an aftermarket player. it will either cover the secondary area with the cassete, or you can get a universal CD pocket, see what your local shop has, make sure you get all your bases covered.
the wire kit will allow teh radio to be installed without cutting the factory harness. This makes install WAY easy, and protects the value (if there is any left) of the vehicle. It has the added bonus of not having to lookup vehicle wiring colors. the harness will come with aftermarket universal wire colors, as will yrou aftermarket radio. you can just match the colors together, one by one, and then plug it in to the factory clip, and itll work immediately. not worth saving $15 over, it will result in hours and hours of extra work.
the antenna adapter is for your car if you have one that doesnt have a standard antenna. old nissan widebody trucks need an adapter, chevy trucks need an adapter, VW needs one (did they make a truck in the 90's?) ford does not needd one, I do not beleive dodge needs one.
piece of cake. if an installer has done more than a dozen of your specific car, it would take him about 15-20 minutes to do the whole job, from teh time he turned off the car after pulling it into the bay.
takes the rest of us a little more time