Welcome to car-seat.org. I'll try to answer a few questions and I also have a few questions for you.
It's great that you already checked the expiration date. I would recommend looking at the Used Car Seat Checklist...
http://www.cpsafety.com/articles/usedseat.aspx. It's a good way to make sure that the seat you are using is safe. It also includes a link to the recalled seats, which is also a good thing to check.
How old and how big is the child that will be using the seat? Will you be using the seat in the rear-facing or forward-facing position at this time? How to install the seat will depend on the age/size of the child and on whether it is installed forward or rear-facing.
Do you have the manual for the car seat? Some of your questions can be answered using the seat. One of the things you will want to check in the manual - and it might also be on the seat itself - is what the weight range is for the harness in the rear-facing and forward-facing. Many of these seats have a 40lb limit on using the harness, but some have a 50lb limit.
In general, the Eddie Bauer seats are good for babies and toddlers that can use the seat in the rear-facing position. It is an okay seat in the forward position, but it is often outgrown early in harness mode by children when they are 3 or 4 years old. Since these children are not mature or big enough to use a booster seat, you have to buy a separate booster seat. Many of these seats do not fit children well in booster mode, so I would recommend only using it as a harness seat.
I'm sure we can answer more specific questions once we know more about the child who will be using the seat.