Amanda

You've asked two questions here.

Q 1) How to search content in the Description field

Q 2) How to make the message box hold more characters.

You don't mention with which entity you are working.  I am going to assume that you are referring to the fields oppo_description and oppo_note of the opportunity entity.

A 1) The Description field for the opportunity is cover by both the quick find and keyword search features so I don't understand what you mean by searching content in the description field.

A 2) The field oppo_description is the datatype nvarchar and its default length in the database is 100.  This creates a max length for this field of 50 characters.  Within the Admin screens for the Opportunity entity the field is defined as a Max Length of 50 and a Entry Width of 30.  Strings longer than 50 Characters will be truncated.
The field oppo_note is the database type nvarchar(max) which allows it to hold   The maximum storage size for this type of field is 2^30-1 characters (2 GB)