You should first try freezing an app to make sure it does not cause problems....and give the phone a workout.....trying all the functions you can think of to make sure it did no harm.
My preference, once you determine to remove an app, is to use Titanium to convert it to a user app. You long press the app in question and a menu pops up where you can make different choices. Once it is converted....you can uninstall it just like any other app.
Keep in mind.......YOU are responsible for everything you do.
Your configuration, and the apps you use, may be different than mine and what works for me may cause a problem for you.
Make sure you have a good backup. I actually made a separate backup on an extra SD card just so I would always be able to put it back to stock.
A launcher overrides the existing home-screen app.....the one with the snap-out menu. You do not remove anything to install a launcher.....just download one from the Market. I am running a launcher called "Go Launcher EX". It is easily removed if you don't like it.....and it's free.
When the new launcher is running my search key brings up Google Search just fine....of course you need to install Google Search from the Market.