I would advise you NOT to get into IPOs. They are very hard to evaluate in terms of price. Also the risks are high because there is no universal proven factors that will tell you if a certain company will succeed. It is true that people who bought in at IPOs for firms like Google and eBay has made a kill, but i personally would not get involved. Even though GM is a restructured company with much of its toxic assets dumped, it could still be pretty risky.
I haven't looked in this IPO in particular, but the general rule of thumb is that if you, as a retail investor, can buy in at published prices, this is a deal you dont wana be involved in, reason being that if this is a good deal, institutional investors would already have snatched up those shares, leaving you with higher prices. I would advise you wait about 2 months, until the volatile prices have stabilized, and do your research on the firm.