transfer from tank to tank
 

i bought a used up and running 75 gallon with a 30 sump reef tank, can i just transfer my rock and stuff from my old tank to my new tank or do i have to do stuff b4 the transfer

Yup, just move it over, save as much original water as possible, prepare some new water day before and leave the used sand behind. If you want to reuse your old sand you'll have to rinse it well before adding to the new tank.