TOKYO, April 24 (Reuters) - Nissan Motor Co. is finalising plans to spend 10-20 billion yen ($86.5-$173 million) to build an assembly plant in Russia with production slated to begin in 2008, the Nihon Keizai business daily reported on Monday. The paper said the factory near St. Petersburg will likely have an initial output capacity of about 20,000 units a year. It would be the second Japanese car maker to produce vehicles in Russia after Toyota Motor Corp. .