I've got some seemingly common issues...pleas help?!?

[Vinman]

ok..here's a noob askin a few questions im sure someone else has answered before..I just haven't had the time to really go back into the archives...anyway....ok...
1. My abs, trac off, and low coolant lights are on, my coolant level is fine, it used to come on then go away, now its on constantly( I noticed whoever had the car before put the cheap non-gm coolant in there, haven't had time or money to have it flushed. My trac control doesn't work, and my brakes used to make it feel like i was skidding on ice when i came to a stop at low speeds, doesn't do that anymore, but im not sure if the abs works, i haven't been daring enough to test it since this problem arose. Also, my buddy who is a mechanic and has been working on gm's for years, tells me to clean out the connections on the hubs...would this work or do i have to shell out the dough for two new hubs?

2.Also, my tpms isn't working, i had a completely flat tire last week and had no idea until someone at work mentioned it to me..I've been having issues with my tires not holding air, I have two snows from a bmw up front, which are fine, but i have two pirellis in the rear which are almost bald, the two from the front(got rid of those) had plugs in em, not sure about the rear...also I did a stupid thing and put green slime in one of the tires and i think that may have messed up the sensor..at least for that wheel, but my other rear tire went flat and i had no notice of low pressure...i know this doesn't replace actually checking the pressure yourself but it has been pretty accurate

3. I have a metal on metal rubbing sound coming from passenger front wheel, i dont think its brakes, because it happens at all speeds, and even breaking, i don't think its the bearing because it doesn't make the typical humm or the wheel doesn't deflect the way it shouldn't. It sounds as though the dust shield (behind the rotor) is hitting it but i don't think thats it..though i haven't had the time to look and see whats up...

4. And lastly, has anyone had any issues with their fuel door not closing completely? I have the one where you actually have to go over to it and open it when you fill up...when i got the car i think it was fine, but recently the door just doesn't want to go flush with the side of the car...is there something soo stupid and easy that im missing or is it actually complicated?

Ahhh...finally done...if anyone has any suggestions...I would be very grateful...cause after seeing the cars on here, i want to start modding, but i won't till she's fixed...Well now im off to work....thanks again all.....