Starting Over Talk - Peer Coaching Support Site

Ok I have a question for a canadian citizen that came to the US to marry and reside here. If you know personally or have info based on people you know that have done this I have a huge favor to ask!

What is the best way to go about this??? So far they know they have to have spent time together here within 2 years of the intended marriage, they need birth certificates, divorce papers and photo id. Is the best way to get a work visa, marry.. then the Canadian spouse go back to Canada and apply for spousal visa OR go with the K1 (K3) fiance visa where they have 3 mo. in order to have the wedding and then apply for citizenship? Or is there another way where the Canadian party can enter the US, work and marry without being sent back for a period of time and where Canada won't deny them entry into the US for 3 or more years?

Also is it best to do it through a US immigration attorney or file on their own?

A lot of questions I know but any assistance in the matter would be greatly appreciated! (and as much detail as possible) Thank you!