Clutch slipping

I have a 1998 Honda CRV, all wheel drive, stick shift, 4 cylinder, with 120,000 miles on it. I recently had the timing belt changed and the brakes repaired. When I press in the clutch, it now feels 'soft' and I have to push it all the way down to the floor before it seems to engage. It will also stick half way up sometimes when I take my foot off.
Approximately how much would it cost to fix the problem, and is this a worthwhile amount of money to invest in a car this old, given that I just spent $1500.00 for the timing belt.
Thank you.