just a point of view but I dont see the point in drilling holes in good solid metal to create potential rust traps - surely you must have seen many a basket case with the rust blobs along the doors and wings where the clips that hold the trims on go.
my angle is to use some silicone type adhesive or trim tape and stick the things on.
if you're determined to use the standard nasty little crappy clip things (once you've eventually sourced them) then make sure you treat the bits you drill with some kind of rust prevention stuff inside and out because no matter how good your paint job is, once the rot sets in you're buggered.
i dont know what the argument will be FOR the clips, but im sure someone can offer a different point of view...
I think rimmers will be able to do the silver coach lines for you.
on the paint for the sills if you're gona do them black (theres various people with different views on whether to do them black or not), after a decent layer of stoneguard and then the body coloured paint, I'd use the same satin black as used on the boot/rear panel. as a reference point, mask off a line about 1cm thick along the top edge of the sill before you paint, leaving a little strip of body colour below the door line visible. I'd strongly advise against fitting the sill trims using clips, in fact i wouldnt bother fitting them at all. In my opinion they look crap an dif fitted with clips they're the worst rust traps of all!!