Okay I'll take a stab at trying to answer until one of the guys that really know these motors see this and chimes in.
Obvious Q's to ask of the dealer is How many LT5's and how often? Did the tech own a ZR-1 or did he go thru the LT5 service course? The Tech would have to be at least a middle aged person, last yr was 95. I'm not trying to be a wise guy, but I would be more interested in how often & how many LT5's his shop actually works on.
The oil leak is coming from where, as you said you saw it when under the car.
If I understand you, your diagnosis is the pan gasket is leaking. If it is you could try to re-torque the pan bolts. You will have to have the car on a lift or up on jack stands. All the pan bolts are okay to get on save the front ones. For those you take the two cross braces off of the car. I think the are the "K" braces, I think. Whatever they're called you see that the forward ends anchor to the cross member that holds the rack and the aft ends look like they hold the motor mounts. The aft ends Do Not hold the motor mounts. I know it don't look that way, but it's true. The motor mounts are on ears just above the braces you have to remove to get at the oil pan bolts at the front edge of the pan. Just take those braces out and you can get on all the bolts. Please be careful and do not over torque the pan bolts. Just put a socket on them and use a T/Q wrench to test for their present T/Q. If they start to move then check the T/Q number and go from there. In order for me not to over T/Q them I used my 1/4" set to test their tightness before I attacked them with my 3/8" T/Q wrench.
Anything else you need just post up!
Oh, sorry forgot.....Welcome to the Brotherhood!
Tom