>1) In large Tables, whitch is the performance difference using SQL-Stored Procedures,
>passing just the procedure's name + parameters using SQLEXEC(), from sending a query
>Statement + parameters to a remote server using pass through.

It is a commonly accepted best practice to use stored procedure for all data access and manipulation.

>Should the responce time increase if the SQL Server Statement is more complex ? If yes how much more time it would take. ( just an idea of time increase )

There's no direct answer to this. The simpliest queries may require a tablescan while a very complex looking query might be solvable via a covering index.

-Mike