Melanoma

Hi there, I haven't posted on here before.  I have had a small mole-like growth on my arm for over a year.  I mentioned it to a Consultant whilst at a skin clinic I attend for regular checks on seborrheic warts, and was told it was a blood neavae, not to worry.  This continued to worry me and I mentioned it regularly to be told it was not a problem.  So a couple of months ago, I paid to be seen privately and was told it was a basal cell carcinoma, no problem, but I was referred to have it removed.  Today, I was told that after examination in the lab, it is a melanoma, and that it is stage 2a, and I now need to have lymph nodes removed.  I am in shock firstly, but now am worried that I am having surgery that I don't really want (ie removal of lymph nodes, what does that mean for my immune system eventually?) and so on.  It is early days, and I haven't got my head around this yet, but what is your advice?