WORLD : Calderon Seated in Costa Rica

<i> From Times Wire Services</i>

A 41-year-old lawyer from a prominent political family took over as president today in the long shadow of Oscar Arias Sanchez, who thrust this country into the global spotlight with his regional peace efforts.

Incoming President Rafael Calderon Fournier acknowledged his predecessor’s international renown but said he will concentrate on internal affairs--without giving short shrift to foreign policy.

Arias spearheaded Central American peace efforts that promoted democracy and sought an end to civil wars. He won the 1987 Nobel Peace Prize for drafting a regional peace plan.

Although originally thrilled with Arias’ fame, many Costa Ricans have now come to feel that he gained it at their expense--by ignoring domestic problems. Even so, he leaves office with an approval rating of 90%.