My vehicle gets to midrange of first gear and the trannsmission feels like it slips,
Have already changed the filter and fluids, would both of the speed sensors cause this issue?

It's possible. Replacing VSS or OSS Sensors is more common for shifting issues in higher gears. Unfortunately, I suspect first gear's clutch pack is shot.

Right on best answer I got yet thanks.
To replace all this the tranny has to come down right?

Yes.