u/Fuzzy-Appa-2482

Hi I'm not a DA and I found an office that is willing to train me on the job. I have no prior experience aside from shadowing other dentists. The doctor is suggesting that I get my x-ray certification and coronal polishing certification. Any suggestions on where I should get it done? How long does the process take? Is it hard? Is it expensive? Any advice? Any help would be appreciated :)