99 Classic multiple questions

Hello, I am new here and I have searched all over on here and google and what not and can't seem to find an answer. So here I am. I have a 99 classic with 6nz and 10 speed rockwell and I have been trying to get all the quirks worked out of this truck. My biggest issue is the speedometer that doesn't work I have located the speed sensor and the wires look like something ripped them from a plug maybe? For the life of me I can't find a plug to put them back into anywhere.. When I bought the truck (used about 3 months ago) I noticed the low air alarm wasn't working (buzzer or light) upon further investigation the buzzer had been removed so I bought a new one at dealer and installed and it is apparently stuck in the alarm position? The alarm will continue to go off all the way to the gov shutoff and I have removed the speaker for temporarily. What would cause the alarm to be stuck on and the low air light to not come on? Next issue I need some help with is the A/C will only work on high, it blows snowballs out the vents but when you turn it to medium or low the fan shuts off? And then finally my next one I can't figure out is when you turn the wipers on they come up and wipe fine but won't go back down to the bottom of the windshield they stop about 7-8" from where they should be. Some of this might be being a little picky about a 20 year old truck but its my first truck and I am extremely proud of it. Any help at all will be very much appreciated as I am just about stuck on these last little issues. Thanks in advance for the help!

 

Thanks guys for the responses! As for the speedometer I figured tracing wires back down out of the cab was my best option I haven't had time yet to do it but that should work. Does anybody know where the fan speed resistor is located? And then lastly I'm not sure if this is supposed to be this way or not but with the AC running the fan clutch appears to lock in and it won't let the truck get over about 140-150° is that correct? I feel lok that's a little cold for the motor to be running? Out on the highway with a load it will get up a little more than that just wanted to check since a motor running not in optimal temperature would cause poor economy. Thanks again guys for all the help!