These types of questions are always best answered by a docotor or pharmacist.
However, phenylephedrin is a decongestant, benadryl is an antihistamine and vicodin is a narcotic pain reliever. The concern would be that both bendryl and the vicodin would cause drowziness on their own. They would magnify that effect when taken together. You might want to take Zyrtec instead of the benadryl as Zyrtec doesn't cause the drowziness that benadryl does. Other than that, they are safe to take together, but don't drive and limit other activities.
Take care.
Your best bet is to check with your pharmacist to see if it's safe to take these meds together - they are definitely your best source for information of this type.