If you're rooted then there are a few roms that are AOSP. Which means vanilla android. Rooting is really simple on the incredible as long as you follow directions. But Rooting also carries risks and voids your warranty. I would say do your homework before you make a decision.

 

First off, please don't pirate apps. It takes a lot of work and time to create the great apps we have and the money developers make from selling their apps are what make it worth their time to create the apps. Pirate enough apps and developers will stop making apps. The only differences most of the time between free and paid versions of apps are the free versions have ads. I have had my phone since last July and I have yet to pay for an app, the free versions are good enough. Not to mention, downloading and installing illegal apps is becoming a better and better way to get malware on your phone. This is not good and you want to avoid this at all costs.

Now, no there is no why to just uninstall or turn off Sense. You can put install launcher on top of Sense though. The two most popular launchers are ADW or LauncherPro. There are free and paid versions of these apps, please don't pirate the paid version. What these apps will do is replace your home screens. Aside from a few elements of Sense like the app drawer, widgets, and lock screen (I think) it will be like Sense is no longer on your phone.

The only way to completely get rid of Sense is to root your phone and flash a new ROM. DO NOT, I repeat, DO NOT do this unless you know what you are doing. Flashing ROMs is a very good way to completely completely ruin or brick your phone if you mess it up. If you want to go through with this, do lots and lots and lots of reading first. If you want to read about rooting and flashing ROMs, check out the All Things Root forum here on Android Forums or check out www.xda-developers.com and check out the Incredible section on the forum. You will find more than enough information in these two places. And welcome to Android Forums.

 

I have edited your post to remove comments about pirating and where you go to do so. As the post above me said, please do not pirate apps. If you are unable to get them yourself, you can always ask your parents - they're not expensive and I'm sure they'd be more than willing to throw you 1 or 2 dollars

 

The recommendation about reading/doing your home work has nothing to do with your age. We just don't want you to brick your phone. All of the questions you asked have been answered a million times. Go spend a few days reading all the root stickies and you'll have a better idea.