Three stockholders have sold their 57 percent interest in Kappa Systems Enc. of Arlington, paving the way for Micronet Services Inc. of Washington to acquire the company.

Micronet this week paid $690,000 ($3.50 a share) for the 197,000 shares of Kappa Systems owned by Kappa Chairman D. G. Munger, President William R. T. Oakes Jr. and James H. Connors Jrs., Kappa announced yesterday.

At the same time, Kappa's directors accepted a merger plan under which Micronet will offer the same $3.50 a share for Kappa's remaining shares, which are traded over the counter.

The merger requires the approval of owners of a majority of Kappa's stock, but Micronet already owns more than half the shares, so ratification of the agreement is only a formality.

Kappa Systems is a diversified professional services and consulting company. Micronet, which is privately held, provides consulting market research and training in information management and office automation.

Munger and Oakes have resigned as chief executives and directors of Kappa Systems, the company announced. Management of Kappa and the two seats on the board have been taken over by Micronet Chairman William Wilson and President Larry Stockett.

Details of the merger plan are expected to be announced to Kappa shareholders within 45 days. Within a month after that, a special stockholders meeting will be held to approve the merger.