I ♥♥♥♥♥♥♥ HAVE TO SHARE THIS
IF YOU USE TASK MANAGER
YOU PROBABLY DO CTRL + ALT + DELETE
THEN GO TO A GIANT WINDOWS THING
AND HIT TASK MANAGER
DO CTRL + SHIFT + ESCAPE
THIS IS INSTANT TASK MANAGER
THIS IS THE BIGGEST DISCOVERY IN THE HISTORY OF THE WORLD

Facepunch search isn't gone, only the button is. The actual function still exists. You can go to the link that the search button (that is now gone) usually takes you by clicking on this link. http://www.facepunch.com/search.php

SVN Installation

1. Download a suitable SVN client. TortoiseSVN is the one this tutorial is written for.
2. Find your "garrysmod" folder (usually C:\Program Files\Steam\SteamApps\[steam_username]\garrysmod\garrysmod\addons).
3. Right-Click on the "addons" folder and select "SVN Checkout".
4. Type the SVN address (example: https://svn.wiremod.com/svn/wiremod) into the first text box and type the full address of your addons folder into the second (see step 2). Username is "anonsvn" and password is also "anonsvn".
5. When it is done downloading, you can delete the .svn file in your "addons" folder.
6. Every so often, right-click on your "addons" folder and select "SVN update" to check for updates to your SVNs.

Alternatively, SVN Tutorial: http://www.facepunch.com/showthread.php?t=688324

There are multiple ways to clean your garrysmod, we shall cover three of them here.
1. Delete almost everything

Go to "C:\Program Files\Steam\steamapps\USERNAME\" ("C:\Program Files (x86)\Steam\steamapps\USERNAME\" on 64-bit; Or where ever you installed steam.) and delete the "\garrysmod\" folder. Note: This will NOT require you to re-download the game; Steam will extract the necessary folders when you next run Garrysmod.
2. Delete ♥♥♥♥♥♥♥ everything

Simply go into your steam games list, right click "Garry's Mod", and click "Delete local content..." , then click OK. Then go to "C:\Program Files\Steam\steamapps\USERNAME\" ("C:\Program Files (x86)\Steam\steamapps\USERNAME\" on 64-bit; Or where ever you installed steam.) and delete the "\garrysmod\" folder. Note: This will require you to re-download the game.
3. Delete unnecessary things

Go to "C:\Program Files\Steam\steamapps\USERNAME\" ("C:\Program Files (x86)\Steam\steamapps\USERNAME\" on 64-bit; Or where ever you installed steam.), Then go into the "\garrysmod\" folder, then go into the "\garrysmod\" folder inside the first one, and delete all the folders and files except:

1. models
2. materials
3. particles
4. screenshots
5. sound
6. shaders

If you wish to keep your addons, don't delete the "\addons\" folder. This will delete your settings, including any custom key-bindings("\cfg\config.cfg"), tool presets("\settings\presets\"), addon data ("\data\"), and gamemodes("\gamemodes\") you have; Don't delete those folders if you want to keep any of those. If you don't want to re-generate your spawn icons, don't delete the "\spawnicons\" folder.