Help with <if> conditionals...

[DiSpy]

I know there were more, but here's a few that were bugging me all week...

How do I use an <if></if> conditional to only show something when there are no posts in a particular forum? (I'd like to put a box at the top with something like "Wow, looks like no one has posted here yet... why not start a topic?")

How do I use <if></if> to have the threads/replies/lastpost columns not show up if it's an external link?

How do I use <if></if> to show or hide stuff from search engines? Or is it easier to just show or hide stuff from all guests? (I'd like to hide sigs, some postbit info, etc)

How do I use <if></if> conditionals to show stuff on a users' postbit ONLY if the field is filled out in their profile? (and/or custom profile fields)
-- I'd like to show standard things like last login date, and secondary usergroup.
-- I'd like to show some custom fields I made, but only if they are filled in.

On a totally separate note, i'd like the archive to show a quick reply box on the relevant pages. Some of my users (including me) will be using the archive (is there anyway to change the name from "archive"?) to view the site using their cellphones/pda's. I have quick reply turned off in the admin panel, but I can turn it on, and then just disable it in the default style with <if></if>, no? Also, anyway to add a <new> icon next to new posts in the archive? ...and are there templates somewhere for the archive, or is all hard coded php files?

THANK YOU!