1) Gov. Mary Fallin (R) -- or, if the special election is declared in early 2015, whoever defeats her in this year's election -- will have to set a special election sometime within 30 days of Coburn resigning, likely in early January. This is not when the special election will be held, but rather when the governor is required to declare the date.
2) A three-day filing period must be held at least 10 days after the special election is declared.
3) The primary must be at least 20 days after the filing period...
4) The primary runoff (if necessary) must be at least 20 days after the primary...
5) And the special election must be held at least 20 days after the runoff.
Now here's the kicker: As election lawyer Adam Bonin notes, Coburn can issue his resignation date early, apparently allowing Fallin to set the election before he resigns and potentially for the same day as the 2014 general election. In that case, Coburn's resignation date would be binding.
Given Coburn's penchant for saving taxpayer's money, it would seem a good bet he would do what he can to avoid the cost of holding a separate special election.
Of course, this is all a long ways off, but you can rest assured the jockeying is already starting.
Updated at 8:50 a.m. This post has been corrected to reflect the possibility of Coburn tendering his resignation early.