<p>Is it better to use a stored procedure or doing it the old way with a connection string and all that good stuff? Our system has been running slow lately and our manager wants us to try to see if we can speed things up a little and we were thinking about changing some of the old database calls over to stored procedures. Is it worth it?</p>

The first thing to do is check the database has all the necessary indexes set up. Analyse where your code is slow, and examine the relevant SQL statements and indexes relating to them. See if you can rewrite the SQL statement to be more efficient. Check that you aren't recompiling an SQL (prepared) statement for every iteration in a loop instead of outside it once.
Moving an SQL statement into a stored procedure isn't going to help if it is grossly inefficient in implementation. However the database will know how to best optimise the SQL and it won't need to do it repeatedly. It can also make the client side code cleaner by turning a complex SQL statement into a simple procedure call.