Just got FF8 PS1 promo for $2, no D1, what to do?

I bought this promo for a pittance but only 3 disks, Should I give up looking for disk 1?
should I just sell the disks?
Buy a regular FF8 D1 and keep it?
Whats it worth with just 2,3 and 4?

I dunno...

I keep a relatively small PS1 game collection.

If you're doing it for the purposes of collecting I'd see if there's just a single disc for sale. If you just wanted to play it the swap trick is easy enough to do. Just burn a disc or play it emulated.

whenever I get a PS1 game I use imgburn to make sure the disks are ok . . .
Having disks 2-4 doesn't really count in my mind as having the thing for collector purposes
I really don't know the chances of me finding disk 1 but they seem slim looking at eBay prices (which seem a tad deluded)

If I get rid then find it within a year I would be annoyed, but sitting there incomplete also will nag at my soul

You could probably just go to a retro game store and possibly get some credit towards the purchase of the game