Sewage Pump Installation
Your going to want to seal that bad boy, it's going to get smelly in there and you really don't want the wonderful fragrance floating throughout the house. The sewage ejectors I am familiar with have a removeable lid on a portion of the top thus allowing the vent pipe to not being effected by service to the motor, if such is not the case then should service be required you can simply cut the vent pipe and install a coupler at that time or use a union.
You do not need to mount the pump on anything just make sure the floats are free and clear of any obstructions down there, again, once that lid is on and sealed you really don't want to open it, it's not pretty in there after the first 'major' use.
Don't forget to use ALL the required parts on the drain side...Backflow Preventor, Union, Gate Valve.