The election must always be made a year in advance ... this has always been the rule so if you want to make the change you must do it with a timely filed return for the next tax year. Wash sales do not come into play when you use the Mark to Market option. Please seek information from your broker ... a face to face conversation where you can ask questions and get immediate answers may be the best thing for your understanding of this matter ... you have about 8 months to get educated.
Read the info under Capital Gains & Losses :
https://www.irs.gov/help/find-information-on-complex-tax-topics
