A replacement pack is about $2,500 from Honda, or this guy will rebuild the pack using packs from wrecked Civics for about $1,200 shipped.
Hybrid-Battery-Repair
I know a person with a Civic Hybrid (148,000 miles) who loves it, but I'm reading a lot of sites on the Internet where users (possibly due to a software upgrade at the dealer) are not seeing the batteries fully charge, and mileage dropping from 50 mpg to the mid 30's. I would certainly do a test drive and make sure it is getting to 8 bars on the battery, that IMA assist is working (and you're getting the mileage you expect), and that after an hour of sitting, the battery isn't down to 4 or 5 bars.