Many years ago I wrote an article on this set and the complexities of collecting it. You should still be able to find the article in the old SCD index.. Even though almost 2 decades have passed since that article was published I stand my ground on saying this was one of the biggest pains in the neck to collect. I often wonder if the guys that produced this set even knew how many different parallel and subsets they were making.
I think that one of the biggest problems was the poor distribution nationally. Just like Topps used the Midwest to field test new products in the old days, so did Wheels with this product. I was lucky, living in Iowa at the time and had access to almost all the different formats of the set but collector friends on the 2 coasts and the South all complained that they never saw any of the Diamond Tributes or Treasure Chests.
In recent years the biggest problem seems to be the fact that many dealers, either through ignorance or simple greed put out the Blue Retail (Topaz) cards as Sapphires and charge accordingly. So a $3.00 Earnhardt becomes a $20 Earnhardt card! ALWAYS CHECK FOR THE X/1099 NUMBER ON THE BOTTOM OF THE REVERSE OF THE CARD!! No number means it is the much cheaper retail blue and not a Sapphire. Also just last week I had to point out to a nationally known dealer that 3 off the cards they were advertising as Treasure Chests did not have the Treasure Chest logo on the front. No logo= not a Treasure Chest.
The inserts, I rate them only a little above average for a couple of reasons. Storage can be a problem with those that have gemstones in them (Birthstones, Crown signatures etc.) and I am sure we have all seen cards with the gemstone missing or glued so poorly onto the card as to be considered a type of misprint. Nice idea defeated by poor execution.
If you are just starting to collect I would not recommend this set as it is a real pain. If you are like me and started back decades ago, well we all have our tribulations to go through.