You should be able to use Automated Actions to create notifications, and you can monitor selected fields for any change.  

Start by enabling developer mode and navigating to Settings / Technical / Automated Actions.

Create a new Automated Action as follows:

(You can add more "watched fields" as required).

You also need to create an email template, something like this:

The ${object.stage_id.name} ${object.name} has been updated
 
Expected revenue is ${object.company_currency.name}${"%.2f" % object.planned_revenue}
 
Notes: ${object.description}
Salesperson: ${object.user_id.name}
 
Lead was created on ${object.create_date}

This will create an email like this:

Email templates can be a little tricky (in my experience), but there are a lot of examples already setup and you should be able to copy logic from one of them. 

More information on Automated Actions