slip out of gear

I have a 1997 with a 3.0 and a 4r44e, and I have an issue with it slipping/ flaring from 1st to 2nd and temperamentally falling out of gear, and all around sluggishness on take off. I was just wondering what might fix it? I’ve been looking into a getting a zip kit, and also getting an epc...

Was about to remove my (badly rusted) shift motor, check out approx. 11 related items, do the pliers thing on the selector shaft just for grins, and generally drive around for a week (or three) in 2HI, sans shift motor... while perusing the U-Pull-It yard, and obsessing over 9 different schemes...