Not a Golf, but I've driven a 2004 A4 1.8T S-Line, same engine right? It wasn't nippy off the line seeing as it's FWD and heavy, but once it got going it felt fast. The quality inside is second to none being an Audi but I felt the handling let it down as it was a bit rolly
Best way would probably be to split them and let them dry. My 98 Glanza units are only held together by screws and a rubber seal, so open it up and check there isn't a hole or split anywhere
You will have a different colour, unless you want two sets of HIDs. One for dipped and one for main beam Also you might have trouble finding 5000k as most people just stock 4300/4500k, 6000k, 8000k, 10000k etc