I said it before, I'll say it again, you'd be much better off making a new 'episode' from the Half-Life universe over remaking Half-Life over again. Granted, it'll all be all 'high-res' content with more detailed environments and such, but ultimately it's still the same game we've played over and over to death. One cool thing would be original HLDM on the source engine, but ultimately I feel it to be a waste of talent IMHO.
Good luck with it anyway.