Just to start off, some of these social buttons do not allow you to use custom images if you want the full functionality of the script (eg: counter).  And some, depending on what you want will require you reading up on the API documentation for each button and customizing the code to your liking.  I'm going to try to break your post down a bit to figure out what the root of your problem is and how to point you in the best direction.

Sadly, most of these don't make any sense to me, nobody states where to insert the meta tags, and none of the code is explained.

What doesn't make any sense?  I don't think any of these require editing meta tags so what are you referring to there?  Can you give us examples of what you would need explained that doesn't make sense to you?

I don't care which format it is in (know that I am developing in XHTML1.0 Transitional),

This won't make much difference in the end.  For instance --> <img ... /> for XHTML, <img ...> for HTML and a bunch of minor differences, in the end it's whatever your page is set to it can be easily programmed to.

I need to be able to modify everything, particularly information such as that which shows up when you share on facebook (the URL, Image and Website information).

Very possible and shouldn't be hard to implement.  What types of information are we talking about?  Is there a backend (eg: blog admin page) where you type the content where it should be generated or entered by the user?  To further expand, what are you trying to add this to: a cart, a blog, custom script?  The more details you can provide the better.

So far it seems like the best way to do this is to have a javascript file,

A lot of the buttons require javascript but most users have this turned on in their browser so it shouldn't be an issue.

Curtis may be a spammer.

I have used a lot of WebAssist plugins for a while but I have not installed any at all into Dreamweaver 5.5. I kept getting frustrated with the way they want to do things for customization.

Each of the social sites has its own API (Application Programming Interface) and wants you to do different things. For most of my clients, I'm simply putting a logo on the website and making that logo into a link thusly:

<a href="http://www.facebook.com/pagecode" target="_blank"><img src="../images/IconFacebook.png" alt="Follow me on Facebook!" width="30" height="30" border="0" align="left" /></a> Follow Client on Facebook!</p>

<p><a href="http://pagecode.blogspot.com/" target="_blank"><img src="../images/blog_logo.png" alt="Follow my Blog" width="30" height="30" align="left" /></a>Read Client's Blog!</p>

I use honest-to-goodness logos for these that I searched for using Google: "logo Facebook," "logo Twitter," "logo Blogger" etc.

Those logos are hosted in my /images folder on the various websites I manage.

While I think it's handy to program to an API to get people to follow someone's Twitter or Facebook account, I have found that most people don't want to just follow someone, they want to see the actual information being released about the person or company first.

My apologies, Curtis. The original poster said that the "Get the Code" button isn't working.

As I stated, I am easing WebAssist out of my plugins; The last I used was CSS Menu Writer and, when I found it next to impossible to get an image-based drop-down menu to work, I went to Project 7. They also had a Google Maps plugin that would position an address on a Google Map, but was not as useful as Google's own iFrame-based method, so after one use of that, I quit using it.

"And in regards to Twitter, I am not trying to get anyone to follow me on Twitter (I dont' have a twitter account either), I want a share button so somone can click on it, it brings them to their twitter page where they can then share my site."

That's what AddThis will do.

DId you try it in only one browser?

I know that IE 8 on my netbook will not respond on their site. (can't get code - can't even preview the buttons), but Firefox will, and so will Opera.