i keep blowing fuses!

You need to buy a digital multimeter and test all the wires for function without simply guessing what wire goes where. 

The parking light fuse blows probably because you have connected your ground to this wire.  It'll test a ground until you turn your lights on, and the fuse blows.

Here's what I recommend doing:  Set your meter to measure DC volts, on a scale of at least 12 volts.  Now, touch the black probe to a ground (antenna, or cigarette lighter rim).  Touch the red probe to the wire you suspect to have constant power- when you find one that shows 12 volts under all conditions, this is your constant.  Now test for your accessory lead- shows power only with the key on.  Take the black wire on your new radio directly to ground (use a screw and ring terminal).  Once you've identified these, set your meter on resistance, and test the remaining wires in pairs until you find some that show around 4 ohms.  These will be your speakers.  Touch a battery to the pairs of speakers and you'll hear a "pop" letting you know which wires are for which speaker.  If the speaker moves out, the wire touching the positive terminal is positive, the other negative.  If the speaker pulls in, it is simply the other way around. 

Yeah, don't use an 18 volt DeWalt battery.