Lash in the cross slide is the amount of movement in the feed dial before you see movement of the cross slide when you reverse direction. The saddle position is fixed by the v groove riding on the lathe way. It cannot move forward or back from that position. It is possible that it could be lifting if the slide block (P/N 917) is loose but it shouldn't have a large effect on lash, if any. Likewise, cross slide gib adjustment, will not materially affect lash if loose. Over-tightening the gib will affect lash by requiring more effort to move the cross slide though. This causes torquing of the lead screw and increased pressure on the thrust bearing which will be seen as lost motion or lash.
You can adjust the thrust bearing preload by moving the cross slide to the rear of the lathe so the lead screw is freed from the nut. Any resistance to rotation of the crank will now be due solely to the thrust bearing preload. Tighten up the preload until you start to feel increased resistance and back it off slightly from there. This should be close to your optimum adjustment. Reengage the cross feed nut by pulling the cross slide towards you as you rotate the crank. If you have difficulty moving the slide, you may have to loosen the gib. Adjust the cross feed nut set screw for a minimum movement of the crank before you feel resistance as you rock the crank back and forth. Grizzly recommends not trying to reduce the lash below .001" as a tighter adjustment increases wear on the components.
Note that having lash in the cross slide is not a terrible thing. Lots of older lathes have significant amounts of lash due to wear of the lead screw or nut and still are capable of doing precision work. If the lash is too great and the gibs are loose, it can contribute to chatter though.
To adjust the gib, I back off all the adjustments so the gib is free. With the cross slide in about the middle of travel, I tighten the center set screw until resistance to movement is observed and back it off slightly ( about 10º). Holding the screw in that position with an Allen wrench, I lock the jam nut. Then I bring the cross slide forward and adjust the rear set screw and finally, I move the cross slide to the rear and adjust the front set screw. Properly adjusted, the cross slide should move freely but there should be no discernible movement of the cross slide if you try to move it from side to side.
I use a similar procedure to adjust the lash and play on the compound.