Welcome to the oil patch! This is a great place to get your feet wet.
Let’s start a bit ahead of your questions. First of all, you need to get the wills probated. If there were no wills, then you need to go through the court in Grady (or the county where your relatives lived) and file the intestate forms and affidavit of heirship forms. OK has rules about who can inherit and in what percent if there are no wills.
How do I figure out if my mineral rights are worth anything? Come back here and ask by section, township and range what activity is going on. The value actually hinges on #2. Was it drilled, are royalties being held by the company or the state for your relatives and now you? Is future drilling pending or likely?
How can I tell if they have been drilled and by whom? Come back here and ask and we can help.
3. Letters come asking to buy or lease, how do I known it’s a good deal and in general, is selling or leasing an actual good option? Post a question, again using section, township and range in the County that you have minerals. Folks here will give you feedback. You can use the search icon (magnifying glass in the upper right corner) to look for your section, township and range and see if someone else already posted. Usual form is 10-6N-6W for example.
4. What power do I really have over the minerals outside of signing the forms that come in? Depending upon what power your grandfather had, you will probably inherit that power. There are several layers. You can have royalty ownership only-that means revenue, but not decision making executive powers; you might only own in a wellbore and not own mineral rights; you might have all executive (decision-making) rights and royalty rights, etc.
Anything else I should know or resources greatly appreciated. Hang in there. You have a lot to learn. The lease a company first presents to you in most likely not in your favor. Most of it is open to negotiation.
I would suggest that you read over the General Discussion archives and current topics in Grady for about the last year or so to catch up on what is going on. Then go the investor presentations for the big companies that are active like Continental Resources, Newfield, Marathon, etc. to see what they are saying.
Ask tons of questions! Do not sign anything unless you understand what it says and understand the consequences of it. Learn about the Oklahoma Corporation Commission and what free data exists there.
Overwhelmed now? We all were. Just be patient with yourself and give yourself time to learn. Don’t let anyone rush you into signing something.