Hello all. I am concerned about our shower and mudpan and really need information and advice on how to move forward. We hired a family member to tile our floors, shower, and around our bathtub. He has experience laying tile, but we knew going into this that he is not a professional, and it would not be perfect, which we were ok with. We did our best to make sure what we wanted done was within his skill set, and had different options in place to ensure that. We also knew that we would be an opportunity for him to gain more experience in different areas. We have had to let him go for a few different reasons. All that is left to do is the shower tile, tub tile, and grout the shower floor tile. At this point, we just want it done and are confident we can do it ourselves, but i have some concerns before we begin. I have read that greenboard is ok to use behind tile in the bathroom, and since we are not tiling up to the ceiling i am not concerned about the weight, but to my understanding it should be sealed with redgaurd first. The green board has been primed and painted, I have no idea why, so i am wondering if that will cause an issue with the redguard and tile? My biggest concern is the shower floor, and i just want check if this is even an issue. Family member built the mudpan, and tiled it, but to our knowledge there is no liner/membrane anywhere in the consruction, just a vapor barrier(paper) underneath. Since we have to seal the marble mosaic before and after we grout, will that waterproof it enough? I was thinking about using a small brush to paint the redguard into the space between wall and mosaic tile after we seal it. Will that help waterproof it, or is it unnecessary?

Any suggestions, tips or advice are greatly appreciated! Here is a picture of the shower floor.