I noticed you had a fisher-price carseat for sale in the <city> craigslist site. What is the date of manufacturer on the carseat? From looking at the carseat pictorial, that fisher price carseat was last produced in 2001 (
http://www.carseat.org/Pictorial/3-Five- Point-np.pdf). That model of carseat has an 8 year expiration date on it which would mean if it was manufactured at the end of 2001, it is expiring at the the end of this year. If it was made earlier then November 2001 though, it is already expired.
Many people think that carseat expiration is just a ploy to get people to buy more carseats, but I think carseat expiration is due to several reasons, not just plastic degrading. Here are my reasons on why I think carseat expiration dates are valid.
1. Plastic does degrade over time. It doesn't magically happen at 5-8 years, but it is a good date guideline, especially if a carseat has been used in a hot car or stored in a hot garage. Here is a youtube video of a 10 year old carseat:
http://www.youtube.com/watch?v=wvCRz7BRAM0
2. Manufacturers make safety upgrades to seats all the time. They want to get older seats that might not meet the new safety guidelines out of the market. Seats made 10 years ago, often had a 20-22 pound rear facing limit on them (this was for convertible seats, not just infant seats). Now, those convertible seats rear face to 30-35 pounds, and are much safer. Older seats used 3 point harnesses or shields to protect a child, and now more seats are using safer 5 point harnesses on seats.
3. After a certain period of time, seats loose manuals, stickers wear off, harnesses get frayed. It is hard to get replacement parts for older carseats. Without good working parts or a good manual, carseats may not be used correctly.
4. Manufacturers put limits on their seats and going beyond those limits might limit the manufacturer's liability if the seat fails to perform properly during a crash.
I hope you will take this information and use it wisely. If the carseat is past it's expiration date, please consider not selling it. Dispose of it by breaking apart the different components and cutting the straps and then put it into a bag before putting it out by the trashcan. This will hopefully keep someone else from taking the seat and using it.