I already have an open Ethernet cable home run available between one of my receivers and my router so if I understand you correctly I'm good to go, correct?
My SWM power supply is located at the above receiver location although the SWM is located eleswhere, far away in the atttic, will this cause me any problems?
Will the typical DirecTv installer understand how to make your configuration work?
I don't want to confuse the issue any more than it is, but you keep referring to running ethernet cable from your router to your reciever. If you look at the diagram provided, that is not the case. With a DECA setup, you do not run ethernet directly from your router to your reciever.
The connection from the router is to a DECA unit (either a white reciver DECA unit with a power supply, or a black Broadband Adapter with a power supply). Alternatively, you could get the CCK, which will pick up your router over wi-fi.
Again, if you look at the diagram, it shows the router connected to a white DECA with power supply, which is then connected by RG6 coaxial cable to the splitter, not the SWM. In the case of this diagram, the SWM is actually in the dish LNB, while it seems like you have a SWM8 in the attic.
So what you need is a run of coaxial from your splitter to somewhere close to your router. In most cases, including yours, these runs already exist, since you have coaxial already going to your recievers, so most people will choose to do this close to their recievers.
I would follow what somebody previously posted. Take the coaxial cable out of the reciver that's close to your router. Add a 2 way splitter. Run one cable from the splitter to a DECA/BBA/CCK with a power supply. Connect your ethernet to the same DECA/BBA (if it's a CCK, you won't need the ethernet, because the CCK is wi-fi). Since you don't have any recievers with a built in DECA (HR24/34) you'll need separate white DECA at each reciever. So, run the other cable from the 2 way splitter back to a different white reciver DECA, and connect the DECA coaxial pigtail to your recievers sat 1 input. Lastly, use a short ethernet patch to connect the DECA and reciever. Repeat that last part with each reciver you have (coaxial from splitter/SWM to white DECA connected to reciever sat 1, ethernet patch).
Long story short, you need a DECA for each reciever, and one more for your router (this can be DECA/BBA/CCK). Nothing connects to the SWM except for the coaxial you already have connected.
There are a lot of different ways to do this, but in reality they are all very similar. Chose a setup that works best for you.