Hello. My GF has been an owner of a '11 Krom/Rogue for a few years now.
Its her daily beater. She normally uses the aux, for music, after apple has changed their proprietary connections overtime. The SUV is pretty much stock, with barely noticeable upgrades, considering it being a "Krom" edition.
I've been eyeing into CarPlay systems and just want to be guided in the right direction. So far a friend introduced me to Pioneer system that has the CarPlay software.
I've looked around the forum specifically for anyone who might have dived into the idea and started a DIY. So far, specifically for our generation Rogue, ive found little.

Was hoping to have anyone who has done the intergration of CarPlay? could you provide some insight on pricing, brand, possibly a DIY, etc.

Looking to upgrade my GF system. New/current IPhone, but cant use b/c the auxillary was her only connection.

We've used FM transmitter, but they can be finicky especially being in a city with multiple radio frequencies.

Thanks for your help and input!!

Welcome to NICOclub!

The solution is to replace the head unit with one that has the features she wants. There's a few write-ups in here on how to that yourself. As for which brand to get, that's a matter preference, and I'd suggest going to a shop that sells them so you can hear the difference and make a better choice.