VA medical coverage vs. Regular Medicare Coverage - What are risks for the patient?

My elderly Dad is experiencing more disability and has been covered by regular medicare insurance + supplemental GAP policy. Based on another's recommendation I began looking into VA possible upgrades for his home for disabled person. I was told he had to have VA PCP (primary care physician). I read that VA coverage and Medicare do not overlap and you're covered over one or the other. Was also told he needed a VA PCP who would then refer him to his 'specialists;. A nurse at on of his Dr's told me VA would offer many more meds and no cost & that you're bills are paid under either one or the other, depending upon which you choose.

I've also been advised don't mess with his coverage if it's working. Been warned the VA could come in an 'take over' his assets? Does anyone have such experience? Does VA try to pry elders from their regular medicare coverage? I could use some additional good info on this topic. thanks PS: Dad is not looking for VA pension and he has Hancock LT care policy. Is it worth hooking up with VA just to get home disability upgrades ? Or will it complicate everything else that seems to be running smoothly? thx.