I attempted to recharge the A/C in my 2000 Blazer only to hear a low hissing from this (I'm going to assume) fitting/valve. I haven't been able to find anywhere stating the name of this part so I can look into replacing it.
And if I'm even able to replace just this or if I'll have to replace the entire hose.

 

think you will changing the entire hose

 

That is a dryer/accumulator line. Have you tried snugging up the fitting? I believe there is an O ring on the end of that line. Haven't been in one for a long time. You will have to have the system vacuumed and make sure it has oil.

 

I did attempt to tighten that fitting a little, but was afraid of breaking the line and it felt pretty tight. I may loosen them up to check for the O ring. Thank you

 

You will have to completely discharge the A/C system before loosening the nut.

 

You can pickup an oring kit off rockauto for a few bucks. I did this on mine before I did my v8 swap and it worked like a charm.
You will have to evac the system before you do anything though.
FOUR SEASONS brand, part number 26742 is what I used

 

Yup common place for an o ring to leak. Get a full o ring kit and do them all at the same time along with the accompanying bits involved in freshening up an A/V and then head to a shop and have then vac and charge it up for you.