Helix 10 ,898, ipilot networking ? And couple other ?'s

I need a little advice on a few things and I always get good info on here so here it is. Presently have a 898c si at console and 797c si at bow. Have a terrova ipilot that is now connected to the 898.
My plan is to put a helix 10 si at console and move the 898 to the bow to replace the 797 . I understand an Ethernet cable will network the finders but what do I do with the Ethernet cable coming from t/m ? Wasn't sure if I need a connection switch or hub or if there is a y cable or something ?
Next question is while I am involved in an install should I purchase a separate di transducer and switch to use two ducers with the helix or just go with the one si transducer that's included? I've been reading about this on here and thinking I might want to do two?.Last question is I already have an external hb gps puk on the boat. Is it worth hooking it up or just use the internal gps ? And if I want to use it how do I hook that up properly with the two units? It and my current units were on my boat when I bought it so not sure how it is hooked up now. The terrova is the only thing I've added myself till now.
sorry about all the questions but I'd like to try to order everything I need in one shot for a smooth install( probly won't happen but I can hope)
thanks!

If you want all three item to communicate and be able to share everything. You will need an ethernet hub Humminbird as-eth-5pxg . Also needed is an adaptor cable for your Helix to hook into the hub. Trolling motor already has ethernet cable. The 898 has an external ethernet connection so adaptor cable is not needed but an ethernet cable is needed. Length to be determined by your layout.

Measure where you are going to install the hub. Then measure from that point to where you are going to install the 898 and the Helix. Try and order cable as close as necessary . Last I checked Humminbirds ethernet cables came in 2' 6' 10' 15' 20' and 25 ' lengths. Have done several of these for friends and family.

External puck is usually a little faster than internal. If your puck is the heading sensor one. It is a distinct advantage over any internal GPS. The networking menu will determine which puck and which transducer will serve which unit.

By the time you are done you will have about 275-400 dollars invested in this upgrade. Depending where and exactly what you end up buying the parts.

Parts List

Quantity Number
1 Ethernet Hub As ETH 5 PXG
2 Ethernet cables exact numbers by the length ordered
1 Ethernet adaptor AS EC QDE

Thanks a lot for the reply and info hays47, I appreciate it! Gonna do a title measuring and get things ordered.