i am having a oil leak and was told that it could be the o ring or the oil coole on 2007 Mazda CX-7

the oil has been leaking for more than 3months. i sometimes smell oil burniing. can i order the parts and have the shop place it.the shop is charging too much and i found parts online cheaper. should i just replace the o ring or the whole oil cooler.
thank you

Asked by for the 2007 Mazda CX-7
It really depends what is leaking. Shops mark up parts, they have to make a profit to stay in business. Shops do not want to fit customer supplied parts because they are not making profit on the part but California law makes them responsible for the part fitted even though they did not supply it.