The most difficult part, assuming you lack the tools, will be refitting the bezel.
Depending on the construction of your particular rep watch, the bezel can usually be pried-off with a thin knife/blade. Sometimes, this can take some time if the bezel is tight or has been affixed with cement (cheap reps are often assembled this way). Just work the knife in a tiny bit in between the bottom of the bezel & top of the case. Move all the way around the case evenly &, eventually, the bezel will come lose & can be lifted off. Sometimes, it takes a few minutes, but, sometimes, it can take 30+ minutes. It all depends on the fit of your particular bezel/case. Once the bezel is off, the crystal, again, assuming it also was not cemented onto the case, should lift off (by hand) or can be gently nudged with the edge of the knife in the same fashion as the bezel (work slowly all the way around the crystal).
To reinstall, simply reverse the procedure - install crystal, then bezel. It is best to have a good caseback press & set of nylon 'pucks' that fit the perimeter of the bezel & perimeter of the caseback to press the bezel back on. However, if you are careful, you may be able to refit the bezel using an appropriately-sized pair of socket wrench sockets (or something similar - any round, cylindrical object with a smooth face that fits will work) & a vice. Just be careful to press gently, slowly & keep the watch centered in the vice so the bezel presses on evenly. Otherwise, if it gets pressed on unevenly, you are likely to warp it, which adds alot of additional headaches. Also, it should be obvious, but just to be clear, the cylinder you use on the bezel side (to press it onto the case) must not come into contact with the crystal as this will crack/crush it. You can probably find youtube videos that show how to press a bezel on to give you an idea of the process & make it easier to find substitutes for the nylon 'pucks'.