exim4 with spamassassin ... confused

[Harry Putnam <reader@newsguy.com>]

After digging around in several wiki pages and other google hits on
'debian exim4 spamassassin'

I'm thoroughly confused by now.

One of the sources:
https://wiki.debian.org/Exim#Spam_scanning

Under the `Spam scanning' header it tells me exim has a default
configuration for spamassassin (-ed HP included with
exim4-daemon-heavy)

I have the `heavy' version installed and working so far as sending
mail.

So, if exim4 has a default config for SA does that mean I need not
edit anything?.... well apparently not....

The cited page goes on after saying the config is default, to tell me what
edits to make.

>From there it starts getting into what seems to be some really complex
settings. 

... is all that necessary... given the config is default?
-------       -------       ---=---       -------       ------- 

Here is another example of the googled material:

http://www.maretmanu.org/homepage/inform/exim-spam.php#spam

Down at the bottom of page is has an example called: 

`All in one'

Is that intended to replace my current /etc/exim4/exim4.conf.template?

It does not really say.
-------       -------       ---=---       -------       ------- 

Any pointers to a basic SA/exim4 setup that leaves less to guess at
would be really appreciated.

I am not an exim4 or SA adept and don't have a keen desire to become
so just to get a working setup that at least puts something into
incoming messages showing a spam analysis.

Any known working examples would be greatly useful.