Field Services Engineer on Windows platform but want to get into open source environment and certify

I would like to certify in open source and possibly become full-time open source fundi. Please assist on where I should start, the path to follow, costs that may be involved etc

It will be hard to answer such a broad question. I would start with some serious internet searching. Here is one place to start.

https://training.linuxfoundation.org/certification/

Best of luck!