Just looked up the model history. That GTX could be an RFI or a DI. Pretty important for goods advice here as the RFI is a 787 motor and the DI is a 947. Yes the computers or MPEM s go out on these fairly common. It's usually just a component of the whole unit and they can sometimes be repaired. Lots of info here on the forum. The GTI is a nice solid simple machine with its 717 carbed motor. The 787 is also a great motor although more complex especially with fuel injection. The 947 on the other hand had some issues but if treated right can be a good engine.
That's a lot of oil if that's all oil. Prob not from the injection lines most likely the oil tank or fittings leaking which happens.
Now all being said you should really get a compression test to know what you're working with. The compression test tells you many things on these older two strokes. I can go into lengths if you'd like. But basically don't buy one for any price without knowing what the compression is.
$1500 could be a great deal IF there are minor issues, leaks, needs new wear rings, cosmetic, compression is good.
$1500 could be an ok deal IF they need more like top end rebuilds.
$1500 could be an ok deal if you can do all the work yourself and they need total rebuild.
If these were on the water and running it would be a different story but as they are there are unknowns that need verified because worst case fixes can get you into a lot of money, several thousand dollars if you need to pay a shop to do the work.
How much are you willing to spend to get them running?