If they are slp they should have numbers as their names
Replace the resources of the same number with your new slps
by clicking "import slp" do this for both. then make your aks file.
If they are aks files then
Go to file menu in mps and click decompile install script then select the aks file and destination folder and start decompiling. then go to that folder there will be some slp files there. Replace them and make aks file