This is interesting. I hope Jo Taylor won't mind if I have a go at it straight away:

"Pretty shepherdess
God grant you good day.
I am taken with a great desire
To become a shepherd
And to learn the skill* of it."

"How can one become a shepherd
Who has nothing to watch over?"
"If I had your love
Well would I watch over it
For I am well skilled in that."

"You shall not have my love, dear
For fear of dishonour
Never a day in my life
Have I been in love
And I do not have the skill of it."

"Sweetheart, fair sweetheart
Do not fear dishonour
For never in my life
Will I leave aside** your love
Never and on no day."

The fair maid ***
Saying, "Sweet darling
If you know the manner
Of the pretty game of love
Then show me the skill of it."

*    tour is "trick", or "knack", strictly speaking.

**   lerray: laisserai? or conceivably a verb related to "lerre", a robber, thief..."will I steal"

*** s'est soubzrise: I can only guess at this. gasped? trembled? (cf. modern Fr. "soubresaut", a sudden emotion, catch of the breath, gasp etc.)

Not an elegant translation, but with luck I've got most of it.

Malcolm