I Thank you all for constructive replies and answers here!
Generaly I do not multitask on cars either, but it seemed to me reasonable to do fluid changes at the same time;
In the process, I accidentally cranked the engine without oil inside, the first time in my driving career, promise
I normally refresh the transmission fluid every 30K and I do go thru the gears, less then 15 sec total, to drain additional 1/2qt of fluid; I know, I know, it may not be a right thing to do, but strangely I've never had a transmission problem with my old car; its combo transmission/engine is in a very good condition to this day, I bet will go on for another 50-60K easily
but again, ill listen and implement your critics as well!