You don't need to install a custom ROM if you don't want to. To actually answer your post:
1 - Search for a sprint tether cab. It's just a few registry edit you need to make it 'safe'. I do not know them off of the top of my head. If you want to use your phone as a wireless hotspot (which is tether 'safe'), you can use the cab
HERE.
2 - Two overclock applications to choose from
HERE. I am trying OCTool now, and it's simple enough.
3- Unlock/flash a custom ROM. Read the stickies in the TP2 CDMA upgrade section.