So Sometimes I want to change the offer promoted or the LP but from what I see I need to always get a new URL when I do so??? This is really annoying for platforms like POF where I have to then manually get each creative with the new URL and hope they all get re-accepted in one try... Am I missing something here? This seems really slow to change a campaign and try a new offer with Prosper202.
I just edit the offer link with the new one (which edits out the old one) but ya... then I need to do a new campaign 
EDIT: NVM. It does seem to still keep tracking it under the proper campaign, I just had to enable "all clicks" in stats. We'll see if this works if I change the lander too later on...
I was wondering the same things when I ran my very first campaign on POF while using prosper, changing each ad's URL individually.
To split test offers, you can simply rotate the offer's urls in Step #3 Campaigns for the campaign you are currently linked to.
As for for split testing landing pages. It's a little more complicated at first where you have to implement it externally with a PHP Script provided by Prosper.
iPyxel's easy to follow LP Split Test Tutorial
BTW, if you doing POF, and have any questions. I would suggest digging through iPyxel's blog first, most of the content is there.
They also do quite a bit of them in follow along video's which makes everything easier to digest.
Hope this helps.
I'm going to do a tutorial about this in a couple of weeks, because I see a lot of people being confused about it - but in the meantime, iPyxel's tutorial is a good one to follow.
I'd recommend setting a rotator up for every campaign, whether you're initially split-testing or not. You can run the rotator script with just a single URL in it. That way, it's easy to switch or add in URLs when you need them - just a matter of changing one line of the rotator script.
If you have any trouble setting that up, reply here and I'll see what I can do to help you out.