You can try and use z4root to root the device. It isn't on the Market any more but it can be found here
Failing that, try SuperOneClick
PS If you change your Sense build LCD density more than just a tiny bit, it will mess up the display (you can always change it back). If you want to use another launcher... go for it.
You also don't need LCD Density changer or similar. Once you have root access, you can just edit the relevant line in the build.prop file in the system folder using the built in text editor. The line is ro.sf.lcd_density=240
Never, ever conform