If frost is building up in the freezer, check first for a break in the door gasket that could be letting in warm, moist air. If the gasket seems sound, a malfunction somewhere in the automatic defrost system could be the culprit.
This DIY repair guide from Sears PartsDirect will show you all the possible causes and how to fix each one: searspartsdirect.com/diy/symptom/refrigerator-repair/1234589/frost-buildup-in-freezer/ref0003
Defrost System Problems troubleshooting video will show you how to determine the issue: searspartsdirect.com/diy/article/refrigerator-wont-cool-troubleshooting-video-defrost-system-problems
Make sure that the ice dispenser chute is closing properly as well.
You can find parts and diagrams on www.SearsPartsDirect.com
, just enter your full model number. If you rather have a professional repair, call Sears Home Services at 1-800-4-MY-HOME.
Hope this helps!