Mike - it depends on loads of things.... what vehicle, first off!
if its a Defender, you shouldn't have to cut any metalwork
If its a Disco 1 or classic Rangie, then you may need to cut the plastic grill.... I'd advise getting a second-hand one from the likes of Gemm or Strathearn or Dalcrue (or almost any other breakers) and cut that one first..... actually, buy two, 'cos the first one will be a real botch-job