Trim cracking

Can you post a photo of what you are calling the trim above the window and door?
For sure the shower roof vent is a standard item available at any RV store.

Go to any of your any local RV dealerships.

Almost all have a camping store inside them and carry all the parts that tend to need replacement along with supplies.

If the part you need is not on the shelf in their store they have a BIG book that you can order anything RV out of! They usually have it shipped the next day to the store.

What I like about buying from them versus online is the guy at the register can tell you WHAT to buy, and HOW to install it. :C

Seeing its a Forest River product, google them for a point of contact. Or a local RV parts place or local dealership I think would be a start.

We are ok with replacing but where would we get the parts

As it is used and almost 10 years old, most likely will have to start replacing parts.