weathered pressure treated deck, which stain and prep?

We just bought a home in Minnesota.  It has a north facing deck of pressure treated wood.  The deck is probably 10? years old and looks like it hasn't been treated in 3-4 years.  I found a partial can of Pittsburgh Ultra waterproofing sealant, which looks like what was last used.  The deck gets full sun and harsh winters.  The sealant has completely worn off 90% of the surface (except under the eves) and there is some minor cracking and cupping, a little mold, and a bit of dirt.   I used Olympic deck wash and gave it a gentle pressure wash, which helped.  Questions:

1) There's still some discoloration/dirt and there's still some sealant on the deck where it's protected under the eves.  Do I need to sand?  Or should I try washing again with another product?

2) Based on what I've read here, I was thinking of trying a semi-transparent oil stain like TWP100 or Armstrong Clark.  Is that the best plan given the environment?  

Thanks, love this site!