Well, actually, this is pretty simple. The pump runs on standard 120 Vac. You do, literally, cut the (offending) plug off, strip some insulation to reveal the 3 wires. There should be a black, white, and green (possibly bare copper) wire. Next buy yourself a plug at the local hardware store.
It should something look like this one:
The one on the right is what you want. There will be several kinds to choose from but spend more than $3-4 to get a decent one...maybe even $5.
Inside the connector, you should find a green screw, silver screw, and a gold/brass screw. Black (hot) wire goes to the gold screw, the silver one gets the white and the green/bare gets the green screw. Here is a good picture tutorial:
How To Replace The Plug On An Extension Cord Or Power Cord
This is really basic electrical stuff that I think anyone can handle.
However, as has already been pointed out, you MUST plug this into an outlet that is GFCI protected. Or you must plug this into a circuit that is protected by a GFCI breaker.
Your next learning phase will be on how to replace a non-GFCI duplex outlet with one that is GFCI protected. Again, this isn't difficult.
Do-it-Yourself : GFCI Receptacle Installation - YouTube is pretty good.
OR you will need to replace the non-GFCI breaker with one that is GFCI protected. Another item that isn't difficult but you need your wits about you.
Google and YouTube are your friends. Do you have a meter that you can use to probe the outlet to make sure power is off?