Should you take diazapam with food prior to minor surgery?

Generally not, unless you prefer the prospect of slipping into Respiratory Arrest.

Valium (Diazepam) is a strong sedative - any surgical procedure, unless you're undergoing an outpatient procedure where the surgery is performed when you're awake, usually will entail some type of either local anesthesia (e.g., Lidocaine), an intravenous "twilight" anesthetic (Fentanyl) which lowers your awareness level to a state where you can't feel much but you can respond to commands (used in Bronchoscopy's, etc.) or complete anesthesia that puts you under. Unless your doctor is aware of what you've taken prior to the procedure, if you have any problems during the surgery, any steps he may need to take to help you could be hindered by him not knowing you took a sedative prior to the procedure.

If you want to do it, then check first - there are many minor operations where your doctor will actually give you Valium or something similar if you ask. But if you don't notify him of what you've taken, he's off the hook if you die, and your next of kin have no legal case for malpractice since you're required to disclose anything you take prior to the operation and sign up to it.