Folks are generally advised against using big chain service places for anything CVT related. Most dealerships, and plenty of indie shops these days, have extensive experience with these CVTs and can be trusted to service them. The level can be checked but you need to have the CVT at the correct temperature and you need to know which port is the check port (there are various plugs on the transmission housing and they’re often confused by inexperienced people). If you know what you’re doing it’s not very time-consuming.
Keep in mind that there are several versions of these CVTs. Each requires a specific Subaru CVT fluid and the exact locations of drain, fill and check plugs varies. I believe your Forester would have the same CVT as the 2.5L Gen 5 Outbacks, but you would want to confirm that by downloading the correct Subaru FSM for your model before attempting anything DIY (which is also advised against unless you’re very confident in your abilities).
