The username and password are just the login credentials for the router along with the DEFAULT WPA key, it's not personal information, and it is totally irrelevant to you using another router!

Ideally you should change both of these!

You need the actual config from the router, i.e. connection settings, credentials, most of this is easy nowadays as all this sort of stuff is "Wizard guided on a CD which your new router should have"

I very much doubt it's the router causing your problem, they don't just "degrade" overtime, you may have another underlying problem, it's worth updating your firmware if you can.

Also are you using an Ethernet or wireless connection?

The MAC (Media Access Control) address is just a unique hard code which every networking device has, which is a crucial part in networks!

Martin