Marin Fairfax Alp 2011 - Can I fit a 11-32t Cassette
I think a disadvantage of the 11-32 cassette are the large gear steps. Also consider that switching from 25 to 28 already makes it 12% easier.

You could (additionally) install smaller chainrings, 52 is quite large and instead of 30 you could go down to 28 or 24. 

You will need a new (longer) chain if you increase cog size, unless you decrease chainring size at the same time or the chain is currently a bit longer than necessary.  A worn chain will work badly on new cogs or chainrings though.