Kenmore refridgerator 106.74254402 freezing.

Basically, the fridge part is freezing things in the back with the setting on 1.
When I looked at it, I noticed the gasket is leaving a small gap about half an inch wide and about half a centimeter thick.

Seeing how this unit is rather old, I assume that replacing the gasket will fix this, however the person who IS paying for it doesn't like the idea of $100 per gasket. (Plan on doing both at the same time.)

This comes down to two questions :
Are there any good cheaper options for the parts?
If I were to do it myself, how difficult would it be? I have watched a few youtube videos of it and have the general idea. It looks like it's more time consuming that anything else.

Just for reference on the repair process after basic precautions are done, it's really just removing the doors, verifying the replacement fits by lying it on top of the current one. Then cutting the old one and gently pulling it out. Finnish cutting through it, go around the door removing it.
Use a putty knife to clear any left over stuff out, and then place the new one down.
Using a non-sharp tool, work on getting a corner in, then do the that's opposite (kiddy-corner) to it. Get the other corners, and work around until it's in place.
After that, re-attach the door.

 

Which gaskets..... the door gaskets ?
They don't have any effect on the fridge freezing things.

 

I might be using the wrong term then, I was going off what the part seems to be called.
I believe it's the seal that goes around the door to keep the cold air in, and the warm air out.

Also, the stuff at the front of the fridge is usually warmer then the rest.