It unscrews, see the ODNU bit written on it, theres an arrow pointing to the left in a clockwise motion. Undo it that way. Use either: Needlenose pliers or hammer and drift or pin spanner or whatever you can fit in there to turn it with.
Yeah theres nothing stopping you... Just make sure they have the same internal diameters (and external if you wanna use an olive on the end) and make sure they're not really soft/flexible or the barb might pop out.
I didn't think the riding was great, I didn't see the efforts of you spending lots of time on the editing and overall I wasn't very impressed. I also think a little modesty goes a long way...