Wireless Modem and Time Capsule

Question

I am upgrading my internet service from RoadRunner Standard, to RoadRunner Lightning.  My current set up has a cable modem with a wire running to Time Capsule, which establishes the wireless network for my home.  Apparently the only way to upgrade is to have them install a Wireless Cable Modem.
In reading some of the posts, it appears that if I want to maintain a Time Capsule-managed wireless network, I will need to run an ethernet cable from the new wireless modem to the Time Capsule.  Now my questions:
1) Since the cable modem will have established one wireless network, does the Time Capsule have to use that same network, or can I use Time Capsule to establish a new (2nd?) wireless network with the same configuration as my current network (ie, network name, password, etc)?
2) are there issues if I have the wireless cable modem with wireless network "A" and the Time Capsule with wireless network "B" right next to each other in the same room?
3)  Are there any special setup/Airport Utility adjustments I need to make, or with the Time Capsule not know or care that I've plugged it into a different cable modem that it was plugged into earlier?
4) I currently have an AirPort Extreme extending my wireless network in a different part of my home.  I assume that if I can get the Time Capsule to establish the same network I'm using now, I won't need to fiddle with any settings on the Extreme, right?
I appreicate anyone who can shed some light on this!!  Thanks!

Answer 1

1) Since the cable modem will have established one wireless network, does the Time Capsule have to use that same network, or can I use Time Capsule to establish a new (2nd?) wireless network with the same configuration as my current network (ie, network name, password, etc)?
Even though the replacement modem is also a router,, it is often possible to turn off NAT and wireless.. I wish cable companies would just stick with a basic modem because the router they supply is often a heap of junk or unsuitable for end user.. do a google for the exact model you get and see. Even if you cannot turn off NAT you will almost always be able to turn off wireless. 
You can use the TC even with the cable modem having both NAT, ie router and wireless. You need to bridge the TC and set the wireless. I personally recommend you set to manual control of channels, on both devices as both will probably be set to auto and this results in all sorts of issues when they are operating so close to each other. Anyway lock at least one of them. There are only 3 available channels in 2.4ghz that do not overlap, 1, 6, 11. It is highly unlikely the cable modem will do 5ghz so that band on the TC can be left on auto. Give 5ghz a separate name and use the TC if possible as the speed is much better.
As far as using different wireless names (SSID) that is up to you.. both can use identical names and security with different channels.. this will give you a roaming effect, where each device connects to the strongest wireless.. But for this to work effectively the two WAP need to be as far apart as possible.
2) are there issues if I have the wireless cable modem with wireless network "A" and the Time Capsule with wireless network "B" right next to each other in the same room? 
Give them as much gap as possible.. but it should not interfere if they set channels correctly.. but make sure they are as far channel wise apart as possible, eg the cable modem uses channel 1 then the TC is using 11. That way the receiver is able to reject the signal of the other device easier.
3)  Are there any special setup/Airport Utility adjustments I need to make, or with the Time Capsule not know or care that I've plugged it into a different cable modem that it was plugged into earlier?
The TC will have to be in bridge if the main cable modem has no way to turn off router. Obviously if you can change it to no NAT and no wireless then you just plug them in.. no changes necessary.
You do need to power down the cable modem each time you plug something different into it, if it is not the router. This is to pick up the new devices MAC address and pass the public IP to it.
4) I currently have an AirPort Extreme extending my wireless network in a different part of my home.  I assume that if I can get the Time Capsule to establish the same network I'm using now, I won't need to fiddle with any settings on the Extreme, right?
No changes will be necessary if the TC is working the same. Obviously if you have to change the wireless name or security etc then you will need to change the AEBS as well.
Do any of the computers connect by ethernet? If so they can be connected directly to the TC. You can then use the TC in place of the AEBS and connect the cable modem to it by using EoP adapters if you cannot pull an ethernet cable that far. There is plenty of opportunity to do a different layout.
But start with seeing if the modem is capable of having NAT turned off. If so then wireless will also be able to be turned off.. they tend not to use the term bridge.. although that is the same.