Very good questions. I am licensed to practice in Virginia, so I can give you information regarding this matter. However, in giving you this information, ethically I must let you know that you are not my client, and no attorney-client relationship is established here.
Although my answers could change after reviewing the deed and the trust (because they may have separate terms that impact the distribution), property can generally be transferred directly to the purchaser from the trust. The Trustees are the grantors on the new deed, and you are named as the grantee on the deed from the trust. In the alternative, the Trustee could distribute to the beneficiaries, and then the beneficiaries sell the property to you. However, that simply creates an extra step and recording fees.
If you are purchasing the real estate from the trust, then properly, the sale proceeds must flow through the trust. The trustee will pay any costs and fees, and then distribute the proceeds to the beneficiaries. It may seem like that is an unnecessary step since your uncle and mother are the beneficiaries. You may think it would be easier to write checks to your mother and uncle instead of to the trust. However, if there is financing involved, your lender will likely require that the trust be paid, since the trust is the seller.
There may be capital gains tax to pay if the value of the residence is greater on the date of sale than it was on the date of your grandmother's death. The capital gains tax liability generally flows to the beneficiaries. That is the only 'income tax' issue I can think of off-hand that would effect this particular transaction. Naturally, the trustee will have to file a fiduciary income tax return (form 1041) and show any capital gains flowing to the beneficiaries.
Other questions I would ask are: was there an appraisal on the real estate? Was there an estate tax return filed? Has the trustee filed income tax returns for the trust? How long ago did your grandmother die? Does the trust give the trustee the authority to sell the real property?
The answers to those questions could alter the general information I have provided.
I would be happy to look at these documents for you. My law firm has offices in Maryland and Northern Virginia.