Crimea is a totally Russian-speaking region. I mean, you can travel for a dozen of days and got heard Ukrainian speech just only once (supposedly from torists from other parts of Ukraine).
I'm speaking here about times when it wasn't controlled by Russia.

I'm not sure if it is good or bad, but I don't perceive crimean speech as having <em>too</em> clear an accent.
Probably that's because many of its inhabitants moved to there from different parts of Russia, some of them recently.

There're some Russian-speaking regions of Ukraine (Donesk, Dnepropetrovs etc), where an accent is pretty clear. Mostly in the intonation, to a lesser extent in pronunciation.
You may meet some of these varieties in Crimea as well.

It's a good idea. Аll residents speak Russian.