I need a new bumper and grill assembly for my 2001 Skoda Octavia (facelift), so I found a Skoda Octavia XL that is being sold in parts, and I wonder would its grill and bumper fit my Octavia? 

To make a pre-facelift grill and bumper fit a facelift car, you'd need the pre-facelift front wings, bonnet, headlights and indicators as well. And then have to insure and be able to sell the resultant frankencar.