Gear Vendors in but big engine problems
Hope you paid by a credit card, if so you might be able to dispute the charge.
But most times the shop will say no warranty but still 2 weeks ? If they did all the work-even install and break in-you have a good case against them.
Could take them to small claims court too-but they will say you should have shut the motor right off-don't you have an idiot light too when theres no oil pressure, a gauge moves slow, you should have both. The shop should have told you that too.