Nedarim 19: Conditional vows regarding Nazirut

Maybe it's the effects of learning Nedarim or maybe it's my mood, but daf 19 seems to begin with the rabbis just bickering.  What about this sort of firstborn animal; what about that sort of forbidden animal?  Doesn't intention count?  Isn't there a difference between sanctity that is born and sanctity that is chosen?  What about the firstborn of a kosher animal versus the firstborn of a non-kosher animal?  And does liquid help us to understand what might be a difficulty?  How might we understand something that is impure that can cause other things to be impure?  

And, by the way, this giving of the firstborn is a tricky game.  We learn in a note that a sheep is given in place of a firstborn male donkey.  If this redemption does not happen, the donkey's neck is broken. What is the lesson in this?  That if G-d does not get the pleasure of the kill, no one gets the benefit of the donkey's life? 

Okay, I think it's my mood.

We learn in another note that there is such a thing as a permanent nazirite.  Such a person may cut his/her hair no more than once each year if it is too heavy for him/her.  S/he must also bring three animals as offerings before returning to be a nazirite.

The rabbis then argue more pointedly about ritual purity with regard to animals, insects and liquids.  This is followed by a description of how one might become a nazirite by making a conditional promise.  The rabbis seem to be helping each other understand the parameters of nazirut through their discussion.  What are the details how a nazirite deals with hair that is heavy?  How would this or other uncertainties affect one's ability to bring offerings?  And if a person vows to be a nazirite like Samson, well, that is impossible - Samson's status was decreed.  One cannot use a vow to create a status equivalent to that of Samson.

The rabbis end our daf with a continuation of their argument.  Do we treat conditional vows regarding nazirut with leniency?  Can vows of nazirut be conditional at all?  The rabbis seem to hold different views on these topics.