I doubt you can hit anything with slugs and a full choke, I have never seen it work anyway.
I would not give over $175 for a 1400 in 90%, or over $200 for a 1400 in 99% condition.
I have owned one in 20 ga, it was junk. I know a couple guys with the 12ga and they have had trouble too. The local hunter safety group uses them (got them nearly free) in 12 and 20, and have had a lot of trouble.
If I bought a 1400 it would be only to have on hand as a loaner gun, or as trade material and the price was really low.
As you guessed I am not a fan of the 1400 at all, none of my experience with them has been positive. For what a 1400 will cost you buy a 1300 combo with a slug barrel, the 1300 is a darn good gun. IMO the 1200 is junk too. If you want to pony up the cash the SuperX2 is a great shotgun, well worth the money!!