Can I have a tummy tuck without hernia repair first?

Without knowing more about your situation it is impossible to answer this question.  In most cases, I repair the hernia at the time of tummy tuck since there is no added incision and the dissection to perform the operation is essentially already done to perform the tummy tuck.  However, not all surgeons are comfortable treating hernias and you may want to make sure that you are seeing a board certified plastic surgeon that is also board certified in general surgery and feels comfortable repairing a hernia at the same time.  Alternatively, you could have two surgeons work at the same time (a plastic surgeon and a general surgeon) or do as two separate operations.  However, in most cases, I don't understand separating into two separate procedures with two anesthesias and two recoveries.  Good Luck.  

Do them together.  It can be fixed at the time of the abdominoplasty.   If it is a large, incarcerated or an otherwise difficult hernia, it may change a bit of what is done to fix it, but this can be determined beforehand by the nature of the hernia on physical examination.