How do I choose a replacement wheel rim? These are my current rims: Wheeltech TD26 by Alex Rims (can't find much info about these online).  I need to replace the rear wheel as it is cracked (cracks on the rims around a few spokes)
It's a 700C disc brake rim with quick releases.  What do I need to consider other than the size of the wheel when choosing a replacement?  I'll likely migrate over the cassette and rotor (if need be).  My knowledge of rims is limited so any help is appreciated!

Here is my bike: https://www.bikes.com/en/bikes/whistler/2015 (Must select Whistler 70 when on the site)
First, you have to decide whether you want to replace the rim (the ring shaped outer part) or entire wheel. If the wheel is otherwise in good shape, swapping the rim is an easy task and a shop should charge less than for a full rebuild.

For wheel you have to match size, axle thickness, spacing and cassette and brake disk interface. Fortunately, for quick releases there is only one common axle and spacing standard. If you want to keep the discs, you will need hub with Centerlock rotor interface. For cassette interface, the common exceptions are 11-speed road, Campagnolo and Sram XD, and your bike doesn't have any of these. In practice this means you'll want a Shimano hub.

If you swap the rim, you'll need to match size, spoke count and ERD, the diameter at spoke holes. Rim width does not need to be exact match, but if you are using the same tires it shouldn't be changed much. A rim with different ERD requires new spokes and relacing the wheel from scratch.