heater core leaks antifreeze in front of driver seat can engihe be damaged

If you overheat the engine, then yes, you can damage it. If it has been overheated, have the heater core fixed or temporarily bypassed and have the head gasket checked for leaks.

you can buy heater core off the web and follow this guys lead: http://www.volvo-forums.com/t22870-1998-volvo-v70-heater-core-replacement-w-pics.htm