Is it safe to get a tummy tuck and a hernia repair the same time? What are the risks?

Thank you for the question. Yes, umbilical hernias can (and should) be repaired at the same time as tummy tuck surgery. Much will depend on the “comfort level” of your plastic surgeon;  in my practice, I repair hernias routinely during tummy tuck surgery. Some plastic surgeons prefer to  ask for the services of a general surgeon.
Generally I suggest that patients start with the American Society of Plastic Surgery and/or the Aesthetic Society of Plastic Surgery to obtain a list of well experienced board-certified plastic surgeons.  Additional certification by the American Board of surgery (General Surgery) should give you additional peace of mind.
Then, I would suggest you visit a few surgeons whose practices concentrate on aesthetic surgery. 
***Ask to see lots of examples of their work and preferably speak/see patients who have had similar procedures done.  Ultimately it will be important that you feel comfortable that your plastic surgeon have a significant/demonstrable experience consistently achieving the types of outcomes you will be pleased with.   
Besides appropriate training and experience (and certification by the American Board of plastic surgery), looking at before/after photographs (and  preferably talking to previous patients) can be very helpful in this selection process.
 
I hope this helps.
 

it is very common to have a hernia repaired at the time of a tummy tuck. How this is done depends on the location of the hernia and the size of it. Even though I have received my board certification in plastic and general surgery, I occasionally have another general surgeon who regularly does complex/revision hernia surgery fix the hernia. Sometimes they fix it laparoscopically, sometimes they do it over the muscle. In both cases, I repair the diastasis and tighten the skin .