The x27 uses a 2in1 ESC/Reciver combo. You'll need a radio/reciever if you put in a new ESC.
With the size of the diffs in that car and their construction, I would caution against even 4s use. Chrome steel coming from china to be used in RC applications is not very durable compared to even sintered steel and my experience with Hosim is their diffs are usually zinc in reality, which is even softer. I don't know how much id trust their advertising unless I cracked one open and looked for myself. I'd stick to 3s unless you really just want to see what will happen. The car will tear itself apart on 6s. Just a fair warning. You will also need a much larger and lower KV motor, which your motor mount may not accept. Id look for a 4068 or a 4074 in the 2000-2200kv range for 4-6s use in that particular application. Jennys RC has some if you poke around for a pretty good deal.
DumboRC makes some pretty good budget radio systems, they use the radiolink protocol so range and reliability is pretty decent. They're multi model memory, so you can bind more than one receiver to a single radio. Very nice if you decide to get more RC's later on.
Link: https://www.amazon.com/DUMBORC-X6-T...ocphy=1012887&hvtargid=pla-823266995214&psc=1
For a 6s capable ESC, it's hard to beat this value from JennysRC. You can still run 3s with this ESC as well. You won't be able to run a 2s Lipo though.
Link: https://jennysrc.com/products/arrma...n-ara8611v6-copy?variant=48703224185109&gQT=1
If you want to run a 2s Lipo at all, then you'll need something like this since the aforementioned ESC will only run 3s-6s. You can NOT use a 4s-6s Lipo on this particular ESC though. This may seem small for a "1/8 scale" and it is... but the Hosim x27 is more like a 1/10 scale. They market it as a "Mini 1/8 scale" but it's nowhere near the size, weight or the build quality to really be considered anything close to a 1/8 scale. Tl;Dr: This ESC will be plenty for this car IMO. It will be an upgrade over the stock one and you can use your stock motor.
Link: https://jennysrc.com/products/arrma...-typhon-ara4302v3?_pos=3&_sid=33519d028&_ss=r