Addition of permission for read/write ability based on topic/blog entry for each user

I am in involved in a customization of Drupal 5.2 for our company. I need the following things to be
done:

1. When a user creates a blog or a forum topic, he/she needs controls to give access to other users
   who would be able to read the blog, read & reply comments etc for each blog/forum topic. The access
   control should be in the format of a) Public or Private b) Company c) Department/Division d) Individ
   ual.

2. Any reply comments or new creation of blog/forum topic should be send as emails to the particular
   user email ids as in the case above.

Please help me in this issue as soon as possible. Thanks for your prompt help.

Regards,
Mnjose