Is Latin and Greek difficult to learn?

Is latin and greek difficult languages to learn for somebody fluent in english and spanish?

Note that I'm curious in learning greek and latin for my own personal uses in writing to greek friends and in reading latin and greek literature. And I'm looking foward to teaching myself rather than take a class.

How can I learn Greek? ?

I already know some Greek given that I have a few Greek friends. I visited Greece this past summer with a Greek friend of mine and now have a growing interest. I want to learn Greek in a sense that I can communicate if I ever return to Greece next summer perhaps. What does one recommend?

How do you write ‘Nikki’ in Greek?

I have several Greek friends named Nikki and I was wondering how you write it in Greek.
Also, what does it mean?

How do you write ‘Nikki’ in Greek?

I have several Greek friends named Nikki, I was wondering how you write Nikki using the Greek alphabet. Thanks.
I just wanted to add, I meant using Greek symbols.