Your 20" is a bit different than my 26" G4 model Hawk. If I am not mistaken however, both models use two blade holders, one for the bottom and the other for the top. You can load the blade either from the top or from the bottom. You can choose the method which works best for you. I removed the arm which is used to hold down the upper rocker assembly and keep the blade down while inserting from the top, so I have gotten into the habit of inserting from the bottom up. Lining up the blade into the top holder is easier for me. This process in most cases required me to get up and be able to look under the work piece to accomplish this task. In the end, I do not mind this extra step because I can move my body around on a regular basis instead of staying in the same position. I just finished a project which had over 400 cuts and it was not that much trouble overall with this method. Some day maybe I will try the top down method to see how I like it.
You can also check to find out if the blade holders have been upgraded to newer/easier to use versions. Mine changed I think 3 - 4 times during the past 3 years and the newer versions have worked better the those in the past.
The link below is from someone who has their G4 for sale with photos and their is also a link to a write up from another user.
http://harrisburg.craigslist.org/tls/1195231002.html
Overall you have a great machine which I believe, once you are able to get a handle on its use, will be a great addition to your shop. Wish I could find a deal like the one you got.
Ron