G'day bushbandit. Can't really suggest anywhere
close to Station Pier to stay, but as D4D said, it depends how far you want to drive on the day. There are some nice spots within an hour of the CBD. A good one up in the Dandenongs is Kurth Kiln
http://parkweb.vic.gov.au/explore/parks/kurth-kiln-r.p./things-to-do/kurth-kiln-picnic-and-camping-groundCheck in for the ferry starts about 2 1/2 hours before sailing, and closes 45mins prior. Having said that we turned up at around 5pm (for a 7:30 departure), and proceeded to spend the next hour and a half sitting on the pier in the car. You really don't need to get there that early. You go through a few security checks (if you have loose gas bottles you will need to declare them, and pick them up at the other end), check in, get your boarding passes and line up on the pier and then wait.....and wait.....and wait
I would suggest arriving an hour before departure, allowing for shi$$y melbourne traffic of course. Doesn't matter if you're one of the last on, as first on/first off doesn't apply here! We were on board and watching cars turning up and driving straight on at around 6:30!
Hope this helps, and enjoy Tassie mate, it's an awesome place!
Cheers
Matt