A couple of hints:

1. There are four different treasures you can find in the game, but only one will be made available in any given playthrough. If you don't like the one that is mentioned in your ancestor's journal, restart. Some treasures are more powerful than others (the Seal of Solomon/Aladdin's Lamp is my personal favorite).

2. Always aim for the easy targets first - there is a chance that they will have a clue that removes a site from a hard target. In other words, if France, England, and Tyrone all have a treasure site, aim for Tyrone first.

3. Diplomacy is an easy option, but it doesn't always succeed. Try using it, especially if you get lucky enough to hire a high ranking diplomat, but be prepared to invade a country. Remember, you get a CB if the country refuses your request!

4. Large countries will have an easier time playing than small ones. You might even be lucky enough to get treasure sites in your own provinces!

5. The mod randomizes each stage as it happens. If you don't mind cheating, save your game just before investigating the last site. Then, if the next stage is in an area you don't like (a powerful country, or far away and wrong religion) reload and try again.