Hi akhst,
Firstly, I'm not familiar with Agilent systems and their columns and guard columns so please take some of this advice with a grain of salt. The first thing I would recommend is getting your images to load properly on the forum (at least I cannot see them). This would help me understand the guard column and accessories. The guard columns my lab purchases from Phenomenex comes with a zero-dead volume fitting that goes between the guard column and the actual column, and I think that this is similar to your integrated connector but I'm not sure without the images or part numbers. This coupling is extremely short and any change in retention would be due to the volume within the cartridge rather than this tiny connector. However, this could be completely different on the Agilent systems. As for removing the end-fittings themselves, this can be a tricky and you might end up completely disturbing the bed mass and causing a void. It seems like you want to have a zero dead-volume connection between column and guard-- making a void would basically nullify any of that work. But that's not to say that depending on the column and person it cannot be done. First I would try and upload the images (unless it's just me) through the recommendation stickied on the front page of this board.