All of a sudden the veins in my thigh are really dark and all up and down my leg and I just had plantar faciitis surgery?

Get it checked out. Without seeing or examining your leg it's impossible to tell. One concern would be a deep clot in a vein that's called a deep vein thrombosis (dvt). This can be a complication of surgery as well as decreased activity. A DVT can lead to a more serious complication called a pulmonary embolus (pe). If untreated it can also lead to vein problems like varicose veins. You should get it checked out asap.