Need help changing URL's on my sites

I have several websites with URL's in the following format:

GW/World/Isthmus_of_Panama
GS/World/Isthmus_of_Panama
GZ/Life/Canis_lupus

First Goal

I want to change all my URL's to lower case and replace the underscores with dashes:

gw/world/isthmus-of-panama
gs/world/isthmus-of-panama
gz/life/canis-lupus

Second Goal

I don't want to lose visitors that continue linking to the old URL's. So if someone types in GZ/Life/Canis_lupus, rather than display a 404 error page, I would like them to be forwarded to gz/life/canis-lupus.

In fact, I'd like all links that have the appropriate characters to work, whether separate words are separated by an underscore, dash or space...

gz/world/isthmus-of-panama
gz/World/Isthmus_of_Panama
gz/World/iTHMUS of_panama

Third Goal

I don't know how this will affect my statistics, but, if possible, I would like to avoid this:

gz/world/new-york - 22 hits
gz/world/new_york 16 hits
gz/world/New York 3 hits

Instead, I'd like to see gz/world/new-york 39 hits.

* * * * *

So imagine someone types in MySite/world/new-yorx. That would fetch a 404 error page.

If they type in MySite/world/New York, the url will default to MySite/world/new-york. (Wikipedia has a similar function.)

At first, I thought I would have to do TWO things: 1) Modify my PHP database query so that it accepts URL variations (upper vs lower case, _, -, space), then 2) modify .htaccess so that any of these accepted URL's default to the preferred URL. But after doing more research, I THINK I can do all of this with .htaccess. Am I right?

If so, can anyone advise me how to modify my .htaccess files? Below is a portion of an .htaccess file from one of my sites. It may have bugs in it, though it works for my current site.

Sorry for the LONG post, and thanks for any tips.

RewriteEngine On
RewriteRule ^test\.htm$ test.php [L]
Options -MultiViews

DirectoryIndex index.php index.html yadda-yadda.pl

php_flag magic_quotes_gpc Off

RewriteRule ^/?world/([a-zA-Z0-9()_/-]+)$ world/index.php?area=$1 [L]
RewriteRule ^/?reference/([a-zA-Z0-9_/-]+)$ reference/index.php?ref=$1 [L]

Code (markup):