Also, there is the very telling soliloquy that Macbeth shares with the audience in Act I, scene vii. He says:
If it were done when 'tis done, then 'twere well
It were done quickly. If the assassination
Could trammel up the consequence...
We'ld jump the life to come.
This is an important moment in which Macbeth is alone onstage with the audience. Lady Macbeth has suggested to Macbeth her scheme, and he has merely answered "We will speak further." But in this speech, he considers the probably consequences of murdering Duncan, and they are not favorable. But still he admits his desire to proceed in order to be King. He concludes:
...I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on the other.
It is at this moment that Lady Macbeth enters and though Macbeth's soliloquy seems to have convinced him not to proceed with the murder ("We will proceed no further in this business"), by the end of the exchange he is decided.
I am settled, and bend up
Each corporal agent to this terrible feat.
So, though he admits the ambition to commit the murder, it does take, as you say, the support and push of Lady Macbeth to bring the deed about.
Yes, there is evidence. In Act 1, sc. 3, after the witches have told Macbeth their prophecies and immediately after Angus and Ross's announcement that Macbeth has been named the new Thane of Cawdor, he considers the possibility of becoming king (ll. 148-163). In that short aside, Macbeth considers the possibility of what it would take to unseat the king. His phrase, "...horrible imaginings.." speaks to the possibility of killing Duncan and all the ramifications of that act. Then Macbeth, just a few lines later calms his tangled thoughts by saying that if his becoming king is meant to be, then it will happen as it should. Then in the next scene of Act 1, Duncan names his son as his successor, the Prince of Cumberland. As soon as he hears this announcement, Macbeth, in another aside says, " - This is a step / On which I must fall down, or else o'erleap, / For in my way it lies." He goes on to ask that no light be shown on his secret desires to be king and what it would take to bring that about. So Macbeth has definitely given thought to becoming king before he even tells his wife about what the witches said.