RadioShack (NYSE:RSH) tumbled to a 52-week low on Monday after announcing the retirement of its chief executive, Julian Day, and weak fourth-quarter preliminary results.

The Fort Worth, Texas-based retailer said it booked net sales for the three months ended Dec. 31 of $1.37 billion, up 4% from $1.32 billion a year ago, virtually matching average analyst estimates polled by Thomson Reuters.

The electronics seller expects to post earnings in the range of 50 cents to 54 cents a share, which would widely miss the Street’s view of 67 cents and would fall below its 2009 earnings of 60 cents.

The company, which is slated to announce full results on Feb. 21, said the losses came on disappointing performance in the company’s T-Mobile business, lower margin wireless handsets and incremental promotional and clearance markdowns, partially offset by higher sales in its wireless platform.

Upon RadioShack CEO Day’s retirement at the company’s annual shareholder meeting in May, current chief financial officer, Jim Gooch, will take over the reigns. Until then, Gooch will continue to serve as head of finance and will take on the additional role of president.

Gooch, 43, joined RadioShack in his current position in August 2006. Prior to that he spent 10 years with Kmart and, subsequently, Sears (NASDAQ:SHD).

Day said the company is well positioned for the future, and noted that this is “the right time” for him to step aside. Gooch, he said, is an “exceptional business executive with a deep understanding” of the business and a clear understanding of where it should go next.

The board has decided to separate the chairman and CEO positions, and has named Daniel R. Feehan, currently the board’s presiding director and member of the company’s board since 2003, as non-executive chairman upon Day’s retirement.

Feehan currently services as CEO of Cash America International.