First welcome to CK5.

Once you get the truck spend the membership fee for site. You will be glad you did you can see pictures and search for more detail info.
The price to me seems high. I paid $1800 for my 1987 with 92,000 miles on it and it had complete service records from day one. My truck is the base model no pw, pl, no cruise or carpet. That being said here are some areas I looked at on my purchase of a Blazer.
Rust on the floor at rear corners by tailgate.
Rust on the tail pan (under tail gate) where hinges are.
Rust on inside area where the seat belts mount to the side by doors near floor.
Rust on floor where front floor meets the door jamb near rockers.
Rust over rear wheel wells.
Rust on the rockers.
Front fenders are easy to buy after markets so I did not worry about them. You can still find NOS (New Old Stock) fenders and metal but you will pay for it.
Here are pictures to help you (I used photobucket so you can see them). I am sure others can add more. You can also go to
http://brochures.slosh.com/ for more info on truck such as sales docs and info from factory. This is a brothers site and a great source too.
over rear wheel well
Floor at drivers feet
Passenger side area where seat belt bolts by floor.
Driver side area where seat belt bolts by floor.
Rear floor by tail gate passenger side.
Rear floor by tail gate drive side.
Where it starts on floor and in yellow tail gate area.
The floor areas to check have arrows.
Hope these help you.
* edit: Silverado had carpet, rear side panels and brushed chrome/silver trim on dash and passenger side insert on dash. Check
http://brochures.slosh.com/ for more details.