Info on Buenos Aires and Argentina please.?

Yes it is possible to visit Montevideo and other Uruguayan cities like Colonia via the River plate. All you have to do is go to the port in Puerto Madero and take the Buquebus which travels everyday from Buenos Aires to Montevideo and back. For tours, just contact any travel agency (there are good ones in malls like Alto Palermo or Galerias Pacifico) and go and visit nice places like Cordoba, Mendoza, Bariloche. If you go further south, go to see the glacier Perito Moreno and some whale watching in Puerto Madryn, peninsula de Valdes.