My step-mother was married to my father 10 years. My Dad passed 10 years ago. Pr…

Ok, let me clarify a couple things first.. I am going to go through a lot of information here as a primer...
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A trust and a will are two entirely separate legal documents that control different assets. A trust is a "living document" that has a trustee that is put in charge of the trust assets for the benefit of the beneficiaries. It can go on indefinitely after the grantor (maker) passes away.
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In contrast, a will only becomes effective when the testator (maker) passes away and controls any assets that were in their name when they passed. It has an executor who is named in the will who has to file a formal probate case to settle the estate and then distribute any assets to the named heirs. A will is a public document once it is admitted to probate and anyone can get a copy of it.
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A trust, however, is completely confidential and isn't filed anywhere. When the grantor (maker) dies, the trust becomes irrevocable and the trustee has a legal duty to deliver copies of the trust to all the named beneficiaries so that they know what it contains. Then the trustee has a duty to distribute the assets in the trust to the beneficiaries.
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When assets are placed into a trust, then the trust owns them, not the person who put them in the trust. So if the house was in a trust, it would have to have been deeded over from father into the trust with a written deed that would be recorded at the local land records office.
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So if the current deed states it is owned by father, then it would be in his estate and subject to his will. If it is in the trust's name, it is an asset of the trust and would be controlled by the terms of the trust.
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With all that said, it sounds like father gave stepmother a "life estate" which gives her the right to live in the house for the rest of her life, but she doesn't actually own it. When she passes, the "remaindermen" (you) would become the full legal owner of the house.
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If there was a will it would have to go through public probate and you would have been notified by the executor of the estate about your interest and any other gifts from the estate.
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Thanks
Barrister

""So whatever the trust stated it holds up to what my father wanted prior to his passing and Stepmom cannot change it, correct?""
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Correct. A trust can only be changed up until the death of the maker.
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""Can I legally request a copy of the trust?""
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Absolutely, and the trustee has a legal duty to provide it. If they refuse, you can file a "motion to compel" in the local probate court and this will force the trustee to appear and explain why they are violating their fiduciary duties to the beneficiaries by not complying with the Uniform Trust Code which states that a trustee has to provide a copy to all beneficiaries when the maker dies.
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""And, can she sell the house?""
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This depends entirely on the terms of the trust. If the trust grants her the right to sell the house, then legally she could and it would terminate the remainderman's interest. This is a power that some grantors give a life tenant so that they could sell trust assets if they need the money to support themselves. But it kind of defeats the point of giving someone a life estate if they have that power, so my bet is that the trust doesn't do so.
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thanks
Barrister

""So to get a copy of the trust, I just send a certified mailer?""
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Correct.
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""If she does not respond in a appropriate time line, I get an attorney to send her a letter?""
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Correct again, and then file the "motion to compel" in the local probate court if she doesn't respond to your or the attorney's letter.
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thanks
Barrister