CV joints leaking grease

I noticed on my truck listed above Triton that there was quite a bit of play. I looked under the vehicle at the CV joints up front and noticed one was spinning grease out when going down the road because grease splatter was noticeable, but the biggest issue I found is where the CV joints connect to the differential and is bolted on are loose in that area. That side is leaking grease more than the other. Is it normal to be loose in that area and what has happened to make it loose? It's where it bolts on to the front differential. I have the truck listed above with a Triton engine 4.1L. I noticed a lot of play from the front and a little noise, so after looking I saw the inner CV joint housing was loose on the driver side. I saw some grease had come out to the housing was very loose. I checked the passenger side and the housing was just a hair loose no grease. So, I took it to a mechanic to get it looked at he said, he didn't see anything wrong with the axles, just said don't let the one that had grease coming out to go dry and he said the play and the noise was part of the differential, and that he doesn't work on differentials. So, I was assuming id need a new differential. I'm not sure well got to pricing them, yeah, outrageously high and most of the mechanic I go to prefer to get their own parts, so it would be new. I'm not sure if it's just the housing where the CV joint bolts on to the differential. Then do I need a new differential? Never the less I spoke to another mechanic I know and assuming the whole differential needed to be replaced I asked him can I just turn this 4 wheel drive into a 2 wheel drive he said, yes, it would be easy that was going on the assumption I needed a whole new differential. So, the question is, do I need a whole new differential or would it be cheaper for the time being to convert it into a 2 wheel drive I'm assuming again by taking the CV axle in the front out and taking the shafts out I don't know any input on this?