1996 Isuzu Rodeo Question Cost of oil leak repair

I recently bought a 1996 Rodeo for my son. Today we took it to get the oil changed at a Valvoline Quick Change and was told there was a significant oil leak ("at the bottom near the the transmission"). The technician said it was a very costly repair, but could not even estimate how much it would be. They also indicated there was also a small leak at the head gasket. I'm planning on having it fixed, but because I do not know what to expect I'm afraid not being familiar with a fair repair cost, I'll get ripped off as I have been in the past. Could you give me a ball-park estimate of what to expect for both repairs?

Thanks!!