If it's a MITCH or ACH you got a great deal. From the description of the pads it sounds like one of these. They retail for about $300+. I still have three of 'em but two were issued. The older PASGT helmet is pretty much phased out. It is heavier and bulkier and uses a suspension system, though some companies have made "upgrades" that convert it to use the pads. I think I still have one or two of those, and they can fetch anywhere from $25 to $50 most places, though unscrupulous sellers may try to get $100 or so.

As for ballistic protection, helmets never were designed to protect against bullets and direct fire projectiles. They are used for protection against indirect such as fragments from artillery. There are stories of pistol and even rifle fire being stopped by Kevlar or even steel helmets, but those survivors were more lucky than most.