Vic,
I think you'll find very few of us that agree with the sewing machine guy about Tri-Flow. He is quite wrong about it.
I have had as many as 75 machines, still have around 60. ALL of them are oiled with Tri-Flow oil and greased where applicable with Tri-Flow grease. I use sewing machine oil on oilable motors and Singer Motor Lube in the motors.
I can leave my machines sit for months on end after cleaning the old oil out and re-oiling them with Tri-Flow and they take right off like I used them yesterday.
I haven't been working on sewing machines for 40 years, but I have been working on mechanical things of many kinds for longer than that. Used lots of oils and greases and have found that Tri-Flow is one of the best.
If you are not going to rewire the motor, and you use heat shrink to replace the crumbled off old insulation you'll find that the wires have suddenly become very stiff and resistant to bending. If you put heat shrink over the two previously heat shrinked wires you might not be able to bend them in the right places to get the motor back together.
It's best to follow Rain's tutorial. His instructions are quite good.
I don't know about the guy you talked to. I'd tend to take what he says with a large grain of salt.
JMHO
Joe