My 2008 has a plug in the trans dipstick tube. It has a plastic tag around it that says "Caution! Use only Chrysler CVT Fluid CVT+4 Other fluids may damage the transmission". There is no mention of voiding the warranty, it's not sealed as a simple twist and pull pops it right off and no seal is shown as broken (being a round pipe and plug, I would imagine if they sealed it, it would have to be like a soda bottle where a ring would detach as you're opening it). Chrysler can't stop you from maintaining your own vehicle. That's against the law. If you do it wrong, they can certainly claim you voided the warranty, so document everything and you'll be good to go.
I've posted this in plenty of other threads, but you can use the oil dipstick to check the fluid level. It won't tell you if you're low or high on fluid, but it will let you see a consistent level. Here's how:
1. The CVT fluid expands/contracts a lot due to temperatures, so you always want to do the check with the transmission full hot. Have the dealer check the level so you know it's correct.
2. Always check it at the same location after say driving home from work in your driveway. The fluid should be around the same temperature after driving home from work just about every time (with the exception of very cold winter days or very hot summer days). It should be a level place, but since this is just a reference check for consistency, it doesn't have to be, but it should always be the same place.
3. Remove and thoroughly clean your oil dipstick.
4. Remove the transmission plug and fully insert and seat the oil dipstick.
5. Remove and take note of the level. Write a note, take a picture, scribe a line, whatever, this is now an "acceptable" level.
6. That level mark can safely lower or raise a little based on different temperatures but that's now your reference mark. If you see it change drastically, get to the dealer to have it checked.