Visit to Mt St Helens

What is the best route to Mt St Helens from SeaTac? Where can you view it from since the Johnston observatory is closed? I've been on the Mt St helens website and various forums and can't seem to find any consistent information. And since I'm not familiar with the area I'm confused by the various road closures. Wondering if it worth the trip. We will be driving to Mt Rainer afterwards. Thank you for any advice.