ISO 14001 individual vs consultant implementation

Yes, you can do it yourself. It probably won't be as fast as with a consultant, but it will be more economical. 

If you decide to go by yourself Advisera can help you:

• You can enroll for free in our online ISO 14001:2015 Lead Implementer Course - https://advisera.com/training/iso-14001-lead-implementer-course/ - first part is about the ISO 14001:2015 foundations, the second part is about good implementation practices.
• You can develop your own documentation, or you can Advisera’s ISO 14001:2015 Documentation Toolkit - https://advisera.com/14001academy/iso-14001-documentation-toolkit/ - fully customizable and with one-on-one online consultation 
• You can access Advisera’s free ISO 14001 materials - https://advisera.com/14001academy/free-downloads/ and our blog with many articles – like these two:
            Article - 4 steps in identification and evaluation of environmental aspects - https://advisera.com/14001academy/knowledgebase/4-steps-in-identification-and-evaluation-of-environmental-aspects/
            Article - Environmental aspect identification and classification - https://advisera.com/14001academy/blog/2019/08/27/key-iso-14001-benefits-to-customers/nowledgebase/environmental-aspect-identification-and-classification/
• You can watch free webinars on demand – ISO 14001Webinars - https://advisera.com/14001academy/webinars/

Probably you will need some help on environmental legislation. Perhaps you can use a economic sector association, or a legal consultant or a environmental legislation software service company.