Split seams can be re-stitched. You can do it yourself if you remove the seat cover, then stitch from the back side. Floss is nylon and STRONG thread for this type of repair. Make sure you have hogsring pliers and hogsrings to re-install. In a pinch, zipties will work in place of hog rings.
I just used regular thread and a big assed needle. Been holding for about a year but now theres other seams letting go. The one I stitched is the ds seat outer bolster seam, I tend to slide in and out of the van and Im really surprised it held.
It looks like the side of of the seat has a pretty good tear, not just a split seam. Looking at your seats it looks like the side bolster will go eventually, and color/texture matching the bottom to the worn/aged back will be nigh unto impossible.
I think the best option is a set of front seat covers from AATLAS1X here on mud, in the merchandise or vendor section, and a front seat drivers cushion from c-dan for ~$150 IIRC. You will have front seats that match and will be in good working order for a long time, versus a piecemeal looking front seat with older portions likely to fail in the not too distant future. You would then require more piecemeal replacement covers that may never match correctly, and it would end up costing more in the long run. At the very least I would replace the seat bottom cushion and the full covers for the drivers seat.
Get the leather kit from the guy that sells them on here. I had mine done by a local shop and it turned out nice, but I will use the kit from here next time. Yes, I plan on a next time. The way I see it, leather is only good for about 5-7 years.
If you want a real economical option, just get a set of custom fabric or cordura seat covers from Great Covers or GT Covers or one of the reputable custom seat cover companies. Use 'em until your ready to replace the drivers seat bottom foam and the leather on the front seats...