hi, i was wandering if its less complicated to change the discs in a hdd instead of the heads.

no

then, i have a segate st3250823a and trying to get a donor. if a find one, just swap plates to recover the data?

I meant it is not 'less complicated' to swap discs, that's the last thing one should do. (apart from slim drives)
But here I must warn U that if U have never done it before there is a very low probability U will succeed.
regards,
pepe

don't swap platters.
If you will swap the heads, most likely you will damage something.
Also, it could be other problems, which you may not be aware of.
If the data on the drive is valuable, send it in to a professional data recovery company.

Agree.

DO NOT swap platters, it is the hardest thing to do.

Also unless you have done it before, DO NOT try to swap heads.

Send to someone who can!

it would be more hard if there are more than 1 disc it is way better to swap heads .