[UPDATE: It looks like you can customize the dock on the bottom of the screen, but only the two icons in the middle. To do this, you much go into your app launcher, and make sure the View Type is on Customizable Grid, which you can change by hitting Menu > View Type > Customizable Grid. While still in the Application launcher, hit Menu > Edit to change the two middle dock icons. Not the most intuitive, but we're glad we have the option! Thanks welshy992 for the tip!]
I did that on my phone way back when it was stock, and all I had to do was hit the gear in the top left corner that enables moving the apps around. Once I did that, all I had to do was drag the two center icons up into the app drawer and drag the two I wanted down. No settings adjustements needed...
GO Launcher works well for me, and then I downloaded "Custom Launcher Icons" You can change the picture, size, color, shape, etc... of any app on your homescreen or drawer. You can even change your dock background. Also with GO launcher, you can scroll your dock left or right so you have more than just the normal 4 or 5 choices. Got GO SMS too, and it works well.
One thing I did have to do though was disable the notifications on the stock messenger app or I would get a notification or tone from GO and the stock SMS. Check it out, see how you like it