The seat has over 2 years left on it, dorel allows for an 8 year expiration on the AOE.
I have that exact seat op,and I love it. I am concerned..do you know the person from whom you purchased it? and by "know" I mean in a "trust your childs life" to this person kind of way, not a casual acquaintance? The seat itself should have never been in any type of accident, and the harness has NEVER been washed or saturated wet. those are biggies. Also, keep in mind this very seat is sold at big lots brand new for $99 or less every day........
You should be able to download the manual from the site.
In fact,I just went and did it, and it downloaded for me just fine!!
Be sure you go to the dorel juvenile site, then the COSCO juvenile site, and then click on "download prodcut instructions" or this link might work for you
http://www.coscojuvenile.com/usa/eng/Instructions
One thing to be very careful of with this seat is that the TOP position, when you pull the red handles all the way up, is NOT to be used with the harness. This is a common mistake, so I just wanted to mention it. It should have imprinted on the shell something to that effect, but sometimes people overlook that. The seat is outgrown once your childs shoulders go higher than the second-highest harness slots, which are low, so most kids are outgrowing this seat by abotu 3 years old. Also, it should NEVER ever be used in booster mode. It places the belt exactly where the lap belt should NOT be (right across the stomach) and is a very dangerous booster.
However, it is a really nice rearfacing seat all the way up to 35 pounds..my 41 inch 4.5 year old JUST outgrew it rearfacing...
if for some reason the manual still wont print for you, let us know...maybe we can truobleshoot again...