Any boot simply keeps dust and moisture (contaminants) out of the moving parts. Without the boot it will somply wear out quicker. Is this inboard or outboard on the steering? Is it at the wheel or underneath the car?

Either one just keeps out dust and most moisture... similar to the boot on a shock absorber. The moving parts will simply wear out quicker... especially in a either a sandy or wet environment. The steering will pregressivly looser (sloppy) until after a long period of time (months?) it would finally begin to feel unstable at freeway speeds. Tire wear will dramatically increase as it gets worse... and steering will be less precise.

You'll need ot remove the tie rod to change the boot...which means you'll then need to get a front end alignment afterwards.... that's the probably the most expensive part of the repair.