Does a member of congress have any special physical access to buildings that receive federal funding?
Sure; members of congress are often given special access to private facilities. This is most likely because businesses that are recipients of government money would like that to continue, and aggravating the people who get to vote on you getting money in the future is unwise.
“No, we’re here as members of Congress, and there are federal dollars that go into this operation. So we have oversight. And we just want to go in and see what your operation looks like.”
Congress does have oversight over how funds are spent, and the congressmen do want to go in and see how this operation is being conducted. Both of these things are true.
I take it that these members of congress think they can go wherever they want if federal funds are used because "they have oversight."
This interpretation from a comment, that congressional representatives have a special right to enter private property, is false. Government agents can ask for consent to search private property without a warrant, but do not have the right to do so without consent. This is a constitutional right, the 4th Amendment:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
The supreme court has specifically held that congressional investigation is subject to constitutional limitations in Watkins v United States:
(a) The power of Congress to conduct investigations, inherent in the legislative process, is broad, but it is not unlimited.
(b) Congress has no general authority to expose the private affairs of individuals without justification in terms of the functions of Congress.
(c) No inquiry is an end in itself; it must be related to, and in furtherance of, a legitimate task of Congress.
(d) The Bill of Rights is applicable to congressional investigations, as it is to all forms of governmental action.
In addition, the Supreme Court has explicitly held that the 4th amendment applies to hotel rooms in Stoner v California, summarized as:
A hotel guest is entitled to the constitutional protection against unreasonable searches and seizures. The hotel clerk had no authority to permit the room search, and the police had no basis to believe that petitioner had authorized the clerk to permit the search.