Impulse info help

I was looking to buy a small truck, and I ran into this car. Fell in love with it as soon as I saw it. 91 Impulse with 50k miles on it for $1500. Something confuses me about it though, and the guy who works at the dealership has no idea on anything about the car. Hell it's the first time I saw one and I know more about it than he does. I've been doing my best to look up as much information about this car as possible before I actually buy it. I'm eh, Guessing it's an XS wagonback model with front wheel drive since it's a '91. What confuses me is the transmission. At first I think it's automatic, but then I see the D4 D3 D2 D1, then the two buttons "MANU" and "ECON" and the little sticker that says "to shift press brake ( or something like that)" So what exactly do these buttons do? I can't seem to find any information about them anywhere because I don't know what I'm really looking for. Another question. I'm not sure if I actually want to fix up this car or not. Should I bother tuning up the engine / painting body / lowering / new tires / rims? Or should I try and find a RS awd for sale and work on that? I saw a picture of a RS hatchback ( I think it was RS) and the guy had removed the hatchback and I thought that looked so sexy. Just any help on these cars will help me alot. Thanks in advance.

Something else I'm wondering, that isn't exactly about an impulse but.. about the wheels I want to put on this car.. I'm really a noobie when it comes to anything about aftermarket-ing/customizing a car and well, the tires I want to put on it, are ones that are wider than normal wheels. The kind that stick out alittle bit past the actual body of the car. I have no idea what the name of these types of wheels are, or what size they would be. I know like 14" 15" 16" are the height of the rim, and from just common sense I'm guessing the x5x6x7 is the width, but I'm not sure the width of the kind of wheels that I'm talking about.

slack