Opel Corsa C 1.7 DTI alternator

Hello compis.
Well, it seems that the alternator of my Corsa has stopped working, since it has the typical symptoms of alternator breakdown.
Since we are in an unemployment time, not finding a work and that, I have decided to change it. I am a handyman and I love the mechanics, but I need vuetra help to do so. I have taken some photos because I put it with it the other day, but my ignorance, prevents me from continuing.
Img607.imageShack.us/img607/5057/tj0l.jpg
In this you see the alternator below right, and the above that is cut because I did not enter the photo, it is the compressor of the a/a.
IMG585.imageShack.us/img585/413/O1ou.jpg
In this, from below, the rear of the alternator is seen, which has connected two tubes that I have no idea what they are.
IMG694.imageShack.us/img694/6280/q9oy.jpg
and in this the front photo by the rear of the alternator.
Ok, my doubts ...
The belt has pulley to tighten it or does the same alternator. And the back of the alternator that lid and two tubes what is it? and finally the steps I have to make to replace the alternator and pulley.
Thank you very much to all and greetings.

Already from the beginning hahaha, the alternator does not tense is the tensioning bearing that is in the first photo and it is automatic, to take out belt you must take a 15 mm key if I remember correctly and turn the bearing from the sentral bolt you have the right if I do not remember, the tubes of the rear are New alternators usually come ready to install, anyway if you do not load well you can repair it without nesting to change it.

Kikemec, thanks for your answer.
In the fron as soon as he arrives, hehehehe.
What is that what is ??
In the depressor when I release it, I suppose it falls oil, correct?
And to get the alternator, I suppose it will be with two screws it carries.
Thanks again, and forgive my ignorance

UP

That's right, oil falls because they are loaded, the bearing is the big one that is on the alternator, looks easy to know the belt with one hand will throw down or above and you will see that only one rosation moves is, and if you then see the crowds of supports and now.