3-tier architecture

Good day everyone,

I am working on a application which will based on the 3-tier architecture. The system concerned to a health insurance marketing purposes. I chose .NET for developing its framework. This framework contains collection of the business objects. Application interface will be developed in the Flash 7.0. The transformation of data through its framework to the interface will do through the web services which will be used as a communication layer between Business Layer (Framework/Buiness Objects) to Presentation Layer (Developed in Flash 7.0).  The Backend will be in SQL Server 2000.

My questions are:
a. I like to hear some comments on the above decided architecture.
b. How to make webservices effective in performance As interface will use them for communication with the Framework (Business Objects) which will do all the retrieving and storing tasks.
c. I prefer to use VB.NET language to write code. Please, give an example of writing a business object which should be prior in performance rather than security. Pick User object as an example.
d. I did some work on the business objects. I have two classes one is doing all the db work and other holds the business rules. When you initiate its object, the business class, it inform the db class to load the required data in a DataSet object and use it to CUD (create, update and delete) tasks. Is this a acceptable approach to do

I have to be sure before continue with this approach. So, please guide through your help.

Thanks for your help, Have a good day.