A: An informal intestate administration may be possible, but I would want to know more informaton before giving you a definitive answer. I would hire an attorney to make sure it's done properly. As a title examiner, I can't tell you the number of times I've come across estates that were improperly administered and required reopening to cure the title defect. I regularly assist clients in your position and would be happy to discuss the matter with you and potentially help you out if you wanted to contact me.
A: Not knowing more details it is difficult to say. If you were to contact me and provide more details, I could probably give you a better answer or provide the assistance you need to give you the results you are after.
A: Presuming your dad died without a will and both of his parents are also deceased, your stepmother would be entitled to the first $150,000, plus half of any balance (i.e., anything remaining above the initial $150,000) of his estate. Not knowing more about the valuations of his property at the time of his death, whether property he owned was owned jointly with your stepmother, and other factors, it is difficult to say what rights you or any of his other children may have.
Often where family members cannot agree on an "in-kind" distribution of property (i.e., Heir A takes a car, Heir B takes a boat, etc.), the personal representative will have to sell the property and distribute the proceeds (this also happens where creditor's claims exceed liquified assets on hand). Your stepmother, being the surviving spouse in this presumptive intestate estate, would have statutory priority to serve as the personal representative. Thus, rather than offering the ability to take certain property you want, she could sell it all and divvy up the proceeds which, based on your question, I presume you do not want either.
Moreover, being that you are a minor, you would need your parent or guardian to pursue the matter on your behalf.