If you did not use force to remove the screws securing the pump, you should not have any problem re-attaching the pump back into your cabinet.
If you are unsure how to go about attaching the different elbows and unions on your pump, you can bring the old pump to Mainland and get them to do it for you, they do sell PVS pipes as well.
If you intend to do that, you will need to get some aeration in your main and tank while you change you pump and also to wait for the silicone to dry on your pipes.
As you have livestocks in your main tank, you may want to allocate 3 air stones in your tank and another 1 air stones in your sump. During this period, do not feed or on your lights.
HTH