drilling the spot welds out of the top lip is really where the trouble lies ... Although that's not really much trouble to be honest, unless the welder decided to almost fully weld, rather than spot weld it on (like he did mine >.<)
Just make sure you have a spot weld drill bit and a grinder to clean up the bottom face. I'd also reccommend some touch up paint (and primer) as you're bound to scratch it having it on the work bench and drilling and grinding it.
That is if you're too poor to just buy a new mk1 bonnet, but for the price it's worth doing it yourself i'd say
As for the grille it's a case of screwing out your old one, and drilling a few holes and screwing in the new one