You cannot, your talking chalk and cheese. You may be able to get close by using the style/graphics and hacking an existing nuke template, but thats all.
I have no idea. The general feeling seems to be Web Mail is a big security risk, and should you ever want to upgrade your Nuke it's no longer supported.
So it may be worth considering whether to use ...
I think the best defence is to jusy to go quietly about your business and try not to upset anyone. I sometimes wonder just how many hacks attacks are perpetuated by the web site owners attitude.
You can do this if you install MS_Analysis which is a great addition to have anyway.
You can search by IP or Nick and it will show you info such as when they last visited IP address bla bla.
It means your not connecting to the data base and that could be several reasons like you aint got one, or you have not created the tables, or your config.php is wrong.