If you switched from cable to Dish or Direct
 

did they have to do any additional wiring?

I assume the sattelite feed is connected to the cable system that is already within the house?

That is normally the way it works. The only wire they have to run is from the Dish to the point where they come into the house (usually the garage). This distance could be long or short depending where they have to mount your Dish. Direct and Dish Network do not aim in the same direction.

I switched TV service from Comcast to DirecTV but kept Comcast internet. DirecTV had to run additional cable to accommodate my situation. There was no extra charge for this.

Yes. Your assumption is correct.

The previous owner had Comcast, and Directv just attached the cables for the satellite, to the house connections in place.

Any issues with mounting the dish to the house?

When I got DirecTV, free installation meant roof mount. However, the independent DirecTV installer wanted to do a pole mount and charge me extra. I insisted on free since I didn't really care how it was mounted. They called HQ and I got a free pole mount. I've also heard that some folks paid extra for cable runs. Stick to your guns. If they advertise free installation then make they don't try to up charge. By the way, installation was very professional and I am very happy with DirecTV.

Switched from Comcast to DirecTV and kept Comcast Internet (it just went up $2 again this month). No additional wiring was needed. They used the existing cable to my Entertainment area and activated a separate line for Comcast Internet. Only took a few minutes. By the way we just love DirecTV. We also got a free pole mount because I refused to let the installer put the dish on the roof.

I had an extra cable run from the low voltage box to my future office during construction, dedicated to cable Internet. DirecTV used the other cables installed. Didn't get any extra charge for pole mount, installer just asked me where I wanted the satellite dish. After having the satellite receiver high on our two story house in MD to clear the trees which made upgrades hard, I wanted the pole mount. Interesting was that up in MD we had 5 LNB's here only one. Just like the original DirecTv before local channels were added. Got DirecTv for SciFi channel.

If your house has older cable, Dish will want to upgrade to cat5 cable.
Which will give better quality HD.