Wow. That's a lot of stuff to hook up. Don't worry about all the printers and other stuff right now. Start with the basics and go from one item to the next one by one. Yes, it will take time since you have so many things to work with and you'll need to do it one at a time. Try to have a day that's quiet so you can work without interuption.

Start with your main computer and set it up. Make sure the internet connection is working via your modem. Depending on your provider they should be able to troubleshoot any internet connections/modems or reset it.

Once you get the internet connection up and you know your main computer is working just fine, check your wifi modem by hooking up one of the laptops. If you need to buy a new wifi modem, do so. Mine blows out every so often. Go through each laptop and other items that need wifi one at a time checking connections. If something isn't working, set it off to the side.

Make sure each item is compatible with 4G including software. Does XP work with 4G?

Your modem should have a site that has your stuff on it to make adjustments and see if the addresses are right and if your security levels like WEP are messing up your connections. If you buy a new modem KEEP the information and write down any numbers/passcodes on the paper. That has saved my sanity several times.

Check your ports to make sure they are working for items that need one.

Check if any firewall software programs are messing with your stuff.

You may need to update drivers.

Make sure you have the right cords for each item. Some cords are interchangable, others aren't.

If you get frustrated take a break and walk away until you are ready to try again. It's not hard, just time consuming going through all your items. If you can, simplify what you need and what you use occasionally.