The front and rear sunroof seals are showing wear on my '82 300D Turbo so I'm thinking of replacing them. They don't leak right now, but I'm not going to wait until they do. So my question is how difficult are they to replace? Do they need some special adhesive or do they just snap into place? PartsShop has the 2 parts, but I can't order them since I'm in Canada. Is the dealer the only source for these two seals?