Is your car facelifted, (does the rear light cluster have a "circle" in it or not?) If it is a facelift the R-design bumper should be a straight swap, if not it's more involved (different headlights, grills, etc)
Front grille I believe any facelift S40/V50 grille will work with a facelift bumper. On a pre-facelift car fitting the S40 "eggcrate" grille is a common upgrade.
I read up on fitting the factory Xenons and it seems like a bit of a minefield, I found a few articles on this topic
https://www.volvoforums.org.uk/showthread.php?t=261883
Also someone who took the factory lights apart and fitted HID bulbs, unfortunately the images are gone
https://www.volvoforums.org.uk/showthread.php?t=262911
The stock lights are pretty rubbish, I've ordered some Osram nightbreakers for mine to see how I get on. If not i'll likely be exploring the HID options myself.
Not sure about the rims myself as personally I stick to OEM designs, but this site looks useful if you trust it!
https://www.wheel-size.com/size/volvo/v50/