Did the tech delete everything off C when he installed it last time? did you have to install any programs again? Depending on answer, we can likely do the same without paying any money out.
I would buy an 8gb USB drive and use the media creation tool to make a USB. Its always handy to use as a boot disk and you can always format USB and use it for something else later. I always have a win 10 installer around, just in case.
I would copy anything off C you don't want to lose. Updates can go wrong so its always handy to have backups
If you having same problem as before i have to assume the tech just got the update to stick, instead of clean installing win 10 as its unusual to get same problems again