Hi back -
I'm guessing that the 'easy' trail you heard about from Riomaggiore to Manarola is the paved Via dell'Amore of the famous "Blue Trail" (Sentiero Azzurro) and the Manarola-to-Corniglia segment of that same trail? Unfortunately both of those segments of the "Blue" are closed and have been so for some years now due to damage/instability. They'll remain so through this season.
The only two segments of the "Blue" which are open are the segments from Corniglia to Vernazza, and Vernazza to Monterosso. There are many other trails in the park although many of those are also very steep. The "Save Vernazza" website has a couple of suggestions for easier alternatives so take a look? You get to that through a link from this page:
http://savevernazza.com/traveladvisortrailupdates/
And here is the linked page: it does not reflect those two closings so ignore info for Manarola>Corniglia, Trail 2, and Riomaggiore>Manarola, Trail 2:
http://savevernazza.com/wp-content/uploads/2013/04/trailmap_new.pdf
You do not need to purchase a park pass for hiking any trail which is not on the "Blue" (noted as Trail 2 on that page).
More good info can be found on the park's website:
http://www.parconazionale5terre.it/Eindex.php
Editing to add: the Corniglia-to-Vernazza segment of the "Blue" might work for all of you so take a look at that one?