Difference between TDY and PCS?

My husband graduated AIT in San Angelo, TX on Thursday (20th) and has been stationed at Fort Meade, MD. We are planning to arrive there early on Monday night (23rd) since he will report on Feb. 2nd. We have to "house hunt." He is driving his own car from TX to VA (his home) on the way to MD and staying with family along the way. Once in MD, we must stay temporarily off base since temporary lodging on base is full. We are trying to figure out how much he gets per diem for just me and him and if we get reimbursed for mileage/gas. Can he get both TDY and PCS travel? Or just one? If so, which one? Thank you!!