Beginning the process of saying goodbye..how do I do this??

For all of you Max the Wonderdog fans out there I have no so good news..As Matthias picked the babies up from the critter hotel on Saturday it was evident that Max was not doing well and had lost a significant amount of weight within a very short amount of time. 1st trip to the vet revealed a low body temperature and swollen abdominal area along with enlargement of the prostate gland, difficulty peeing and when he did it was dark in color.. labs were drawn, 2 injections were given..an antibiotic and 1 for pain, along with contrast to be given every 2 hours..2nd day was xay day and the films revealed that Max has tumors in his lungs and bladder along with 4 to 5 stones..also in his bladder..for now he is comfortable, still eating and drinking and getting around okay..has to pee several more times a day than usual since he cannot empty his bladder completely but it is lighter in color than 2 days ago..he now takes 3 new medications..an antibiotic, a steriod, and a paste that may help to dissolve the stones..as he is 14 now and has had 3 surgeries in the past 3.5 years we have opted not to put him through anything other than oral medications for treatment..I came home early from Kaiserslautern and will be spending every moment I can with him from now on..he has been my constant source of unconditional love for more than a decade and in his last weeks or hopefully longer I will be here for him.. as long as he is comfortable we will let nature take it's course..call it a selfish move on my part but I need a little more time with this little dog with the crooked legs and the big attitude that stole my heart...a little more time to learn how to say goodbye..