New to Hummers-Rear Air Suspension Problem

[tHUMpson]

Hi all, I have a 2004 H2 which I purchased back at the beginning of October. I am getting the "Service Rear Air Suspension" code on my dash. Everytime I turn off the vehicle and get out I can literally hear the air coming out of the suspension. Where do I start on repairing this problem? Is it better to switch over to coils? What is the price difference? Trying to evaluate my options. If someone could even just give me a link to a thread talking about this issue I'd appreciate that bc it's obviously something that gets discussed a lot on here.

Also, I was TIG welding last week and shocked myself while I had my keys in my pocket and somehow shorted the keyless entry with the high frequency setting on the welder (I know it's not the battery bc I went to Radioshack and had it tested). Are there aftermarket keyless entry devices or do I need to go through GM?

Thanks, looking forward to being part of this forum.