frigidare side by side stop cooling totally?

fridge/freezer stopped cooling totally. shut-off for 3 days and seems to be ok. had frost/ice build-up on back panel of freezer about half way up inside. what is the problem, or is there a problem? don't want to reload food into it and loose it again. is there any tech. support to ask these questions to, that won't rob you for an answer. Frigidare; mod. glrs234za; ser. la13312738; side by side