Wow, that's quite the commute. Traffic and your time will be the biggest concerns. You can probably make it up Hwy 167 to Hwy 18 and then cut over to I-5, but at that time of day traffic can be a nightmare both ways. When I lived in Federal Way (Twin Lakes) and commuted to downtown Seattle via Metro it took one hour 20 minutes into town, one hour and 40 minutes back out.
Still, if you can get out of actually driving and use the bus service, you'll save a fortune in gas and wear and tear. There are a lot of "Park & Ride" lots in the south end that make it easy and affordable. That way if you're caught in nasty traffic you'll at least be able to relax a little.
