Yes and yes! One can choose to swap/switch their 5 Wartoad cavalry for anything else of $35 Kickstarter value. That will be done during the Pledge Manager.
And in the case the $30K Stretch Goal gets unlocked and the backer has picked a GOLD pledge reward level, then the additional $35 can also be swapped/switched.
Correct. Regardless of the army a backer pledges for (Shieldmaidens, Forest Goblins, Talliareum, Orcs or Ogres), the prices are always the same:
1 x Raiding Party = $50
1 x Starter Army = $100
1 x Garrison Army = $150
1 x Campaign Army = $200
During the pledge manager you will be given a "Comments" section. In that section you can ask to swap any boxes of hard plastic for another, the person dealing with your pledge will see to help you out :-)
Don't see the answer to your question? Ask the project creator directly.