Unless its a major change, you can typically get away with just updating a specific component of the apache/mysql/php chain. The only thing I see as "kinda" wrong, is that doc_root isn't really required when you're building a module for the PHP.
The second error I wouldn't worry about the first part. It's simply detecting no valid domain and reverting to an IP address. 192.168/16 is an internal subnet. If it actually configures against that, you may need to remove it if your machine is DHCP (which it could very well be). I wouldn't think that its stupid enough to bind an ip address though, so that would probably toss that quite regularly. I'd assume it should cause no real problems otherwise.
The second one is your problem. It cannot establish a socket on port 80 to listen to. Either there is already something listening on port 80 (quite a number of applications do by default) or you have a firewall tool blocking your connection attempt. Check your netstat -abo and look for the :80 in use. You can also use the netstat -ao | find ":80 ", and take the associated pid and check the tasklist for the associated program.
header('HTTP/1.1 420 Enhance Your Calm');