What is Reddit's opinion of Eco-Fused Screen Replacement Kit Compatible with Samsung Galaxy S3 Including Replacement Glass/Tool Kit/Adhesive Sticker Tape/Tweezers/Microfiber Cleaning Cloth/Instruction Manual?

From 3.5 billion Reddit comments

Replacing both the screen and digitizer is usually really easy. In this instance, it appears the screen/digitizer combo is fairly hard to come by (couldn't find it easily on Amazon), which is why the heat gun/hair dryer is involved (the glass is glued to the digitizer, and both sit over the LCD screen).

So, replacing just the glass should be pretty easy, just a little touchier. You'll have to heat the glass such that it will separate from the digitizer, then glue the new glass onto the digitizer. This appears to be a great inexpensive choice for doing a replacement. A lot of the reviews offer great advice on how to replace it as well.

TL;DR Overall, I would say:
Skill required: Very Low
Patience and attention to detail required: High
Risk of damaging the digitizer during repair: Medium-low, if you get impatient
Risk of damaging the rest of the phone: Really low

DIY for less than $20.