If you have a HAZMAT endorsement, then you should know the rules already. If you don't have a HAZMAT endorsement, then you can't haul HAZMAT, anyway.
HAZMAT is defined as hazardous materials that must be placarded. If it's HAZMAT, but not in a placardable amount, it ain't HAZMAT, and you can haul it without a HAZMAT endorsement. There are some materials that are placardable only if they weight 1001 pounds or more, but at 1000 pounds or less, it's not placardable, and thus is not HAZMAT, and therefore you don't need a HAZMAT endorsement to haul it.
So, to answer your original question of,
"For a sprinter/cargo van what are the rules and regs for hauling haz-mat", the answer is, the rules are exactly the same for Sprinters and vans as for any other vehicle, except that if you aren't placarded as a Sprinter or van (or station wagon or Prius), you aren't a commercial vehicle. If you're placarded, you're a commercial vehicle (and are instantly DOT regulated), and you must comply with all the rules and regulations of a commercial motor vehicle, including scaling and logging (and actually observing the correct HOS regulations).
I use the term myself, but there is actually no such thing as non-placardable HAZMAT, as in the case of the single 55 gallon drum of paint. I call it that, because it refers to material that is not HAZMAT, but
would be if it were 1001 pounds or more. Now, there are HAZMAT materials that are placardable in any amount at all, even one pound, or one ounce (like plutonium, for example), but for the most part, few of those things can be carried in a van in the first place, because they must be physically separated from the driver (inhilation hazards, explosives, some poisons, etc.).
As for your friend, if he had been pulled over and was actually carrying placardable HAZMAT, he'd be in deep doo-doo, and so would his carrier. If you pick up something that has HAZMAT labels on the freight, check the BOL to see how it's labeled, and the weight. For example, a skid of 5 gallon buckets of HAZMAT paint will have HAZMAT placard on each bucket, but that in and of itself doesn't make it HAZMAT. If it weighs more than 1000 pounds it is, but if it's 1000 pounds or less it's not, and it should say whether it is or not on the BOL. If it's material that isn't placardable at less then 1001 pounds, and the BOL has the HAZMAT column checked, make 'em change the BOL to reflect the non-HAZMAT nature of the freight.
Not sure what "Level 3" is, it all depends on the UN# of the material itself. There's PG III (Packing Group), and there's Class 3, which is the flammable liquids. His 6 drums were probably Class 3 Flammable Liquids, and if so were almost certainly more than 1001 pounds. Most paint drums are in the 500-700 pound per-drum range, but some of the base paints and polymers are half that. But most of the bases and polymers aren't usually regulated, regardless of the amount (except for a reportable quantity in case of a spill).
In vans, most often the confusion over HAZMAT or not comes with paints, solvents and things like batteries (of which RLENT has a great story he can relate).
I highly recommend getting a HAZMAT endorsement, even if you never haul HAZMAT, or at least studying that part of the Driver's License Manual in your state and then taking the practice tests at
Commercial Drivers' License (CDL) Sample Tests (an awesome resource). That way you'll know what you're dealing with, you'll know what's in the truck next to you on the highway, you'll know what to do and what not to do in case of an emergency, you'll know how to read the HMCP, you'll know lots of things.
so should I get the book or not?
