I build all my desktops (every 3-4 years) and save around 400$, which equates to about 100$/hr when it's all said and done. PC's are simple to install now, everything's basically plug and play, and if you do any kind of work/gaming on your desktop where you may need additional power for the future, it's easily customizable.
To OP, back up everything important and start your OS from scratch. Last thing you want is conflicting drivers giving you blue screens when you could have just done it right the first time. I'd probably just fdisk my entire C drive and reinstall from there, all of this is easily youtubed/googled.
Never done an AMD->intel swap but just make sure your mobo is compatible with all your accessories(ram/videocard/etc.) Also, you probably already did this, but you may want to splurge on your mobo a bit. Upgradability/customization that seems overkill now may be extremely beneficial 1-2 years down the road with the way tech's advancing. I remember when 512mb of ram was a lot.