Billy#Sn9501$

Hi I am new to this form group I am working on a 97 Monte Carlo that my mother bought brand new she has about 80,000 miles on it now we had the upper and lower intake and plenum gaskets replaced about 3 months ago because of an oil leak and out of nowhere the engine loses all oil pressure the oil light comes on and engine starts to tick and dies. So I do a lot of my own mechanic work so I secured the engine dropped down the cradle with the help of a family member replaced the oil pump the oil pump rod appeared to be in good condition it went up into the socket that it holds itself into under the intake I'm assuming by the camshafts start the engine up it is pumping some oil it's throwing oil on the dipstick but nothing is coming to the top of the motor lifters are collapsed but I don't believe the bearings are hurt yet it has only been started a couple times very briefly can anyone tell me what would cause this issue and where I should go next again this is my mom's car she bought brand new and 98 that has 80,000 original miles it has been very well taken care of so please if you can help any advice would be very much appreciated I just would like to have some knowledge before tearing into the engine any farther or if it is even worth it in advance thanks again.