Learning to fix your own phone can be a fun experience and the skills you learn may be even more valuable in the future. If you are careful, focussed, and go slow, it is likely you will be just fine replacing your own screen. However there is also a small possibility you may damage your phone. That's why I would always recommend that a first time do-it-yourselfer has a backup plan first.
First backup your data. Then wait until you can afford a new phone before you purchase the replacement part for your 6s. Absolutely give the repair a try! Worst case, you will have saved enough money and can walk right into the Apple store to buy a 7/8/X if you fail. Even if you fail, that experience in itself is valuable.
Mall kiosks are often the single lowest quality repair you can get. This is coming from someone who has been repairing phones for 12 years, but even I started out in a mall kiosk. I guarantee you that the 19 year old at the mall kiosk taught themselves how to repair without much guidance from a seasoned professional. Mall kiosks do not pay to train people. They hire cheap, buy cheap tools, and stock cheap parts.
An Ifixit screen will be an average-to-good quality aftermarket part, but it will probably be a higher grade than the mall part.
If you definitely want a professional to take over, find a brick and mortar shop that specialized in cell phone repair. Don't go to any place that is brand new. Look for an established business with lost of reviews. Yelp reviews are filtered and tend to hide the majority of potential reviews. Google maps reviews are totally unfiltered and give a better representation of the business.
The quality of screen found at an independent shop can vary based on the market. For an iPhone 6s, our business can buy $25, $35, $45, and $60 screens. The $25 screen I can buy is the same trash anyone can buy on eBay for $29. The $35 or $45 screen is more commonly what you would find from Ifixit or a mall kiosk. There are decent aftermarkets that will work fine but won't be 100% as bright or colorful as you want. Some business choose to buy a part for around $60 that really will be as good as the Apple store screen. These unfortunately cannot be found on eBay or Amazon. Typically only independent shops with good suppliers can give you an Aftermarket that looks as good as the original. We would charge $109 for this type of repair compared to Apple's $149. So, when you see a shop advertising a $90 or $75 repair for for 6s, they are more likely using a $25 or $35, lower grade part.
Trust your instincts when choosing a local shop, and trust the reputation they have built in your area.