One starting point....
I would FIRST get a firm-as-reasonable bid for the work from a yard professional, with a rough written outline of what they were going to do. You should be seated when this document is presented.
There are various ways to fix a spongy balsa deck, ranging from injecting epoxy into a bunch of holes drilled into the coring, after a lengthly drying out.... Or... You can remove the deck surface, route out the offending core, and then lay down new coring and then layers of glass and then paint and put on new non skid. If maintaining the factory non skid is vital to you, fix it from the inside....
All have been done. The later method is the messiest by far.
The price you pay for the boat should reflect the value of the work needed. For comparison, an awesome E-27, with a diesel and a lot new gear sold in PDX this spring for around 13K. It was a turn-key boat. I have seen neglected ones for half that, and they might have been overpriced....
"Choose wisely" as the knight said when Indy contemplated which cup was the Grail.....
You may want to also subscribe to the YachtList, as this very topic is being discussed today.
http://www.xs4all.nl/~erkooi/YL/index.html
This is the oldest boatbuilding-oriented discussion group on the 'net.
Best of luck,
Loren in PDX
ps: here are pics of such a project, from the Sailnet FTP archive:
ftp://ftp.sailnet.com/ericson/foredeck/