I have to do a similar mod to my '73 since it was an auto on the column car. For what it's worth, I did some research on the bottom collar and started a thread.
Bottom collar for 4 speed key out function - auto to manual conversion
Don't think the above really matters to you though since you don't have the key lock? I want mine to work like my '74 so I really wanted the bottom collar to function.
You will probably need to pull the column to get the shift tube comes out as it is way too long to do it in the car. Maybe you can pull it out the top if you cut the stuff at the bottom off? Not sure, I will look at the tube I pulled out of one my spare columns.
They aren't hard to disassemble. Biggest issue is the later cars with the steering wheel lock since the lock plate has a pressed in pin that is difficult to pound out if you don't have the column on the bench. I had problems with the set screw that held the lower collar to the shift tube and had to drill it out but I wasn't planning to save the collar so it didn't really matter to me. Other than that, just some screws and snap rings. I really doubt you will have difficulty figuring it out.