Whole-Home and cable internet...

1. No, your cable internet cannot share the same coax cable with DirecTV.
2. Yes, they'll run their own coax cables. 

Thanks so much!  Some follow on questions if I may to your #2:

1a.  Does that mean DirecTV will rewire all coax outlets so that there's two connectors?  

1b.  Or do they just add an additional coax to those where they're placing boxes?

2.  What does DirecTV charge for this effort?

1a.  No.  But they can if you pay extra. 

1b.  Yep.  Typically they'll wrap the cables from the dish along the exterior of your house, through an attic or crawl space, then drill through the adjacent wall to the Receiver/DVR location.  Fishing cables inside walls with nice wall plates costs extra.  

2.  I'm not sure what they charge. 

I just had an install done and have cox cable.  It was very simple.  The installer simply took the Cox coax from outside that was connected to a splitter that ran to the tv's and the internet and connected it directly to the internet coax.  He then connected the satellite coax from the dish to the splitter with the tv connections.  No problem.

thanks, guys.

brillo. i'm not sure i understand. it sounds like you're saying that two coax existed outside the house (one for internet .. one for tv). even if this was true in my case, it's inside the house that is the problem where only one coax connector exists, and Whole-Home and cable internet can't both use the same line.

No, he's not saying that. 

First, you need to decide if you want SWM or dual coax cables run to each room.  SWM will make use of your pre-existing coax in the walls providing they are RG6 and home runs.  Whatever you order, ensure you demand "in writting" (and have them provide you a copy via email before you agree), that your will get the specific setup/equipment you want.  Example: "Two HR24 DVR's, One H24 reciever, and SWM installed"  This would give you the ability to record four programs at once and watch all of those programs from any location.  It's just an example.

Typically you have coax cables installed in newer homes (within the past 7 years or so) that run individual lines from a central spot to each room, these are called home runs and I suspect you have that since you have a functioning Cable Internet.  What the installer does is disconnect all but the single line at your cable junction box (splitter) from the rest of the house system and leaves that on the Cox Cable connection.  The remaining connections will be connected to a special connection (looks like a splitter) to which any room having a DTV Receiver will be connected.  If you desire a DTV connection in the room where your Cable Modem is located, the installer will run a single wire for that.

My advice is to ensure you buy HR24 DVRs as there are two benefits:  They have built-in DECA (ethernet over the coax cable) and they are smaller.  Using the HR24, you can link several together and you can use the HD reciever in other rooms to watch recorded programs on the HR24.  I have an HR21, HR23, and HR24.  They are all connected via ethernet but if I could replace my HR21 and HR23 with HR24's I could get rid of the wired ethernet.  Read up on the capabilities of the equipment and I suspect you will go for a package that gives you the most bang for the buck but make sure you get what you think you are getting.

Joe:

You don't need to replace your HR21 and HR23 to use DECA, they just need external DECA modules. You can't 'order' a specific receiver... you order an HD DVR or a regular HD receiver and they'll bring whatever model the installer has available... all will be SWiM and WHDVR/MRV compatible, but not necessarily a particulr model. You can't decide whether or not you get SWiM either... most HD installs will be SWiM now, and if you order WHDVR they must use SWiM to be DECA and WHDVR compatible.

sungam:

  You are correct, sorry about the mis-information.  Now for some playful banter...  When I ordered my last IRD I was asked if I wanted SWM (that was 2 months ago) and I was given the impression (I could be wrong) that SWM was the direction DTV was going, especially for a new install.  As for which hardware you get, you can request it specifically provided they ship your the IRDs directly and then the installed comes to hook it all up.  Maybe that is specific for an area?  If you can't get specific equipment, buy it from a place like WeakKnees.com and you will get what you want but you will not get free equipment or maybe some other promotion you desire.

I'm sure you are correct in everything you have said, but maybe like you said, specifiy you want WHDVR/MRV to get the proper equipment, if that's the route you want to go.