I've been thinking about picking up the post reactions mod.  I have a couple of questions. 

1) I don't suppose there is a trial period? If this doesn't do what we're looking for am I just rolling the dice with the cost of the mod? 

2) Is the install for SMF 2.1.1 pretty straight forward.  Is the install like any other mod or are there extra steps involved to get it working?  

1. There is no trial period, if there are outstanding problems a refund could be issued.

2. It's pretty simple indeed, but there are a few file edits.

Can you be more specific about the file edits?

I'm not interested in paying someone to install or maintain something on my forum. 

Are the edits simple?  Will they have to be done every time the forum is updated? Are the edits documented in the installation instructions well enough that someone who is fairly literate with the forum software can follow along? 

Yes, they are simple and you don't need to re do them unless you replace the files.