You really think so do you.
Not if the machine has been compromised by malware and you don't know it, as you give up this information.
You can change them but if someone really wanted to come after your set-up on the wireless side, none of it means anything, particularly about the IP from the ISP being changed. They have already hacked the wireless on the router and they would know what the IP is from the ISP. And more and more people are finding out about the tools used to hack a wireless system. It don't take a genius to figure it out as more and more users are using wireless.
You're setting there with a wireless set-up and you're expecting some kind of security, then what can I say about it.
How you're going to get attacked is someone with happy fingers clinking on unknown emails or dubious URL(s) that install things on the machine that compromise the machine and they have control of the machine. None of this other stuff you're talking about means anything, nothing, if they have control of the machine.
They can also do this on the wireless side of the router and attack and install things on a wired or wireless machine as they are most likely wide open to attack.
At the very least, if the router has a syslog that you can use Wallwatcher (free) so you can see what traffic is leaving the router to remote IP(s) for possible dubious connections, then you should implement it. You shouldn't sit there and fly blind if you can help it, as you don't even know what traffic is leaving the network/router.
You should try to implement safehex as much as possible.