Early Methodist preachers in America
The Wesley brothers were famously missionaries in North America before they set about their mission in Britain. Once the movement was established in Britain preachers were sent out to the North American colonies and following Independence John Wesley responded to a need for ministers in the new nation.
Family historians in America sometimes get in contact because they understand that their ancestor crossed the Atlantic as a Methodist preacher and would like to know more about this person.
There is a useful guide online to this type of question at http://genealogy.about.com/od/church_records/tp/Historical-Methodist-Church-Records-And-Archives.htm
Preachers sent out before independence are listed in the Minutes of Conference until 1776 http://www.archive.org/details/minutesofmethodi00wesl
There is a good list of ministers who served before 1840 at the end of Volume 4 of The History of the Methodist Episcopal Church http://hdl.handle.net/2027/mdp.39015005672798
As always, if the relative in question was a LOCAL preacher their Methodist life in this country is more difficult to trace.
Finally, the United Methodist Church has an active General Commission on Archives and History, who would be very happy to help http://www.gcah.org/