i have i a 1990 lexus ls400, today while i was changing the car battery i accidently put the negitive to the positve and then when i plugged it sparks came flying out and i had a feeling that i burnt something.. becuase noting works exept my engine please give me suggestions for what to do!! thank you

I would check your fuses first to see if you have blown them.

yep, you blew your 50A (ish) battery fuse. Open up your fuse box in your engine bay, big black box. And it should be red(i think) and screwed in. There will be a drawing of the fuses anyway on the back of the fuse box lid. unscrew it, hold it up to a light, and then go buy a new one, cause im almost positive its blown