About five years. He was appointed in May of 1784 to the position, then spent June touring the eastern US, then left July 5th with his daughter "Patsy" (Martha, his oldest) and James, the brother of Sally Hemings. They arrived in August.

In May of 1789 he attended the opening of the Estates-General at Versailles. In June he helped Marquis de Layfayette to pen a bill of rights, which the Marquis would use for the document of rights he proposed to the assembly in July. Also in July the riots started and on the 14th the Bastille would be stormed, which he was not a part of. There were also "secret" meetings at Jefferson's residence, the Hotel de Langeac, in order to draft a constitution.

Sept 28 1789 Jefferson, Patsy, Polly (who he sent for after arriving in Paris and was his only other surviving daughter at that point, having lost yet another while he was away, the poor child succumbing to whooping cough with her cousin back in Virginia) and her handmaid, a young lady named Sally Hemings and her brother James who was brought to learn French "cookery". While he was confirmed as Washington's choice for Sec of State on Sept 26, two days before setting sail, he did not find out until November and reluctantly accepted in February. He had desperately hoped to return to Monticello, but it would be another 20 years before would be permitted to retire (though he tried to retire again in 1794 for a brief time).

He did not fight in the French Revolution at all and at that stage in his life was a soldier of the pen, not the sword.

Happy to answer any q's about the trip or his time in France, but the short answer is five years and no.

E cause I forgot to add James in the return trip