Understand how you feel, my husband was diagnosed 2 years ago, totally out the blue, and we were shell-shocked. But there is lots of hope and lots of support. When you say 'tumour on the left hand side' do you mean of the prostate itself? There is the specialist nurse phone service here , you might find that useful too.
My husband is doing really well after surgery and radiotherapy which he had access to as part of a clinical trial called 'RADICALS' - do ask about what clinical research is going on at the hospital or elsewhere that might be useful -a really important question but people may not think of it at the start.
Take several deep breaths, write everything down, read up ( great info here and on Macmillan site), ask ANY question you have - tell them your worries - no question or worry is silly. They will have heard it all before! Your Dr /twam will probably have one or more clinical nurse specialists( CNS) - they can be a lifeline - so do ask about that if you have not met that person yet.