93 Auto Transmission question

Hi: Recently had my truck start the hard shift/slip going into 1st and 2nd, have read most of the posts covering this but most relate to newer models than mine. I am lucky enough to have a dipstick and when warm the level looks good. Can anyone give me some direction concerning fluid replacement(process, how many quarts) as my my mechanic just started 2 weeks vacation and I am not interested in going far with this happening. I would like to dump and replace the fluid myself as a starter to see if it helps. The voltmeter is reading good and since I have had it the shifter has been sloppy when putting the shifter into drive.

Thanks alot.