Is it better to spend additional $600 to replace oil pump or donate the car?

Tough call, but i say fix it considering the work already performed is actually a plus and all the more reason to keep the car on the road. Otherwise you loose all of that as well. That is kinda unusual for the oil pump just to go out but stuff happens! These are in fact very durable engines, i know because i see them run to well over 300k all the time with little repair and not very much maintenance. No telling how many miles one would go if it were 'properly' maintained, by the book, which no one does! Is the rest of car in pretty good shape, overall? How many miles on it?

I also own and maintain a 1999 camry, and yes their are some issues due to age, but if your car has been as dependable as my v6 has been 150000+miles,it is worth the trouble an time you may need to do more homework on the problems and replacement parts.also find a mechanic that's capable and trust worthy.

Oil pump is easy to fix but a pain to dig down into the area. I replaced my seals in my toyota and it took a while but wasn't hard. Buy some parts online or at an auto parts store and watch some youtube videos on how to do it. There is a great how to change waterpump, oil pump seals and everything online for the 1999 camry. I found it somewhere.