concurrent insert and update

I will be running two concurrent ssis packages.  Each package will take files from different servers  and insert it to the same table and update the same table.  There are keys defined in this table to prevent duplicates.  I am not doing bulk insert.  I am checking if the same file exists and if it does not exist, I insert.  My question is, is this normal way to do things? We are using SQL server 2008 R2.  Do I have to specifically do locks or SQL server will handle it by itself?