There is almost nothing that can "go wrong". It's a Sanden compressor, a dryer, an evaporator/blower, a condensor and some hoses. They don't make anything, just package the components. Just check the warranty. Are you buying directly from Coldmaster? The $420 on Coldmaster website has NO compressor. The Ebay is $425. The Coldmaster site has a $445. It has THREE air outlets. The Ebay one I saw has ONLY TWO air outlets.
So where is this $420 kit and what is the part number?
The Ebay listing says 1 year warranty. Could not find anything on their website. You would want to know the specifics on the warranty.
Their Ebay sales are in the thousands and they have a 99.4% positive. Pretty good.
The Negative feedbacks on Ebay are all answered, that is a good sign. However, they are all answered by an Asian, broken English person. As though they are overseas possibly. So this all could be a Chinese company with a FL warehouse. FYI FWIW.
You can buy an actual Vintage (60's-70's) under dash/in dash unit and buy all those components anywhere and plumb it.