Good to hear that he had the paracentesis. Those sound like normal things to check for. If the doctor suspected cancer, he would test some of the fluid specifically for cancerous cells. If that test is positive, he should also order an alpha fetoprotein (AFP) level done through blood work and also an MRI or CT scan with contrast of his liver.
As for the temp, post transplant is 101 degrees, which indicates a sign of possible infection and should be checked out. But I think it also depends somewhat on what is normal for the patient. My temp is usually around 97, so a temp of 100 would be alarming to me. I don't think you need to worry unless it reaches at least 100.
Hugs,
Connie