I was changing the springs with the heads off the car, at this point I decided to clean the valves one by one so i pulled out the head and never take care abouth the position

... a friend of mine told me that now the heads an valves need to go to the machine shop.

¿this is correct? or Can I put the valves no matter the position.

Thanks

 

If they are apart, lap them and keep them in position after lapping. I usually write the cylinder number on the valve head and I also use the GM organizer tray. Lapping should provide a good seal, just make sure you thoroughly clean them afterwards.