Three letter, dictionary word, singular, generic, male name, acronym, brandable that could be used in a wide range of niches - these are all positives with the domain that I can see.
There are plenty of .com.au websites that have 'guy' as part of the domain name, and for some of these it would be a suitable upgrade.
I would estimate mid 4 figures right through to the 5 figure range depending on the buyer. Not in the same ball park, but as an aside, guy.com sold for one million USD in late 2007.
As an initial step, I would put up a make offer page using a site like Bodis.com to monitor how much traffic it gets, where the traffic is coming from and to see if you get any offers.
All the best with it.