A 460w power supply is likely enough as they tend to recommend higher than necessary so the end user doesn’t run into any issues. But if you don’t have the 2 black 6-pin connectors, and you have a computer store nearby, it might be a good idea to upgrade. It depends how much power the CPU/Motherboard is using, but more than likely 460w is enough.
You should be able to get it working though check the box for a 4-pin to 6-pin adapter as darthviper mentioned, if there are 2 of them you just need to connect it up. If not then you will need to upgrade for sure.
There shouldn’t be any other issues though replacing a power supply is usually fairly straightforward, just make sure to take a picture or two showing all of the wires plugged in so you remember to plug in all of the wires in the same places when it is replaced.
I can find you a video tutorial showing how to replace one if you’d like, there are quite a few of them on Youtube if you search for “how to replace a PC power supply”. Hope that helps 