Man,
I'm not sure about parking in Seattle.... However, you're talking to the right guy about transit in Seattle. I work for Pierce Transit in Tacoma, according to my computer, if you go to the Bellevue Transit Center at NE 6th & 108th Ave NE (Bay 11), you can pick up the Sound Transit Seattle Express Bus Route#550 @ 2:20pm, 2:50pm or 3:20pm to the Pioneer Square Station, and you're about two blocks away from Bass NW. (go to street level, Walk a short distance NW on 3RD AVE.
Turn left on JAMES ST. Walk 1 approx. 1 block SW on a significant grade on JAMES ST.
Total walking is 0.18 miles.
It's about a 25 minute bus ride. Costs $2.00 each way. To return, go into the Pioneer Square Station (It's an underground station on the opposite side that you came out of) Go to Bay D @ 4:15, 4:45, or 5:15pm and get back on the Sound Transit #550 to Bellevue. It sounds a lot more complicated that it is..... But, if you give the guys at Bass NW a call once you're at the station, they can reel you in.
Enjoy