Wayne Dalton is a spring that is inside a long metal tube or conduit. They break, and then the opener can't lift the door, because it's heavy. That's why it does like you describe, it goes up a bit, then falls.
They are notorious for not lasting as long as normal spring, which is a big fat 4" spring that is much shorter and exposed above your garage door.
Wayne dalton thought it would be a good idea to make the spring just 1" or so or less, but make it the entire length of the door, and it's contained in a conduit, so it 'seems' safer to a homeowner. But, as you can guess, an thin 1" spring is not going to last as long as a fat 4" spring.
You need a new spring. Maybe the technician didn't use clear verbiage, but you just need a new spring, not a 'conversion' of any kind. Get another quote.
How much was the quote? A new spring can be upwards of $400
Both of my wayne daltons busted within a year of each other in a <10 year old house.
Now I have a normal fat spring system.
Call
https://overheaddoorhouston.com/wayne dalton spring (inside the tube)
typical, longer lasting spring (exposed)