Help with GSM relay/switch setup for automatic car starter?

I'm very new to this whole arena and this would be my first microcontroller/relay/etc. setup I've ever done. It seems rather straight forward, in that, a GSM relay/switch would have, what I'd expect to be a pre-paid GSM Sim card activated (won't need a lot of time on the account because the "transactions" would be very short, no?) that is connected to a cannibalized OEM FOB for the automatic starter and so when the signal is sent from a phone, the switch opens, activates the original FOB, and starts the car.

I found this link and there's only, what seems to be, ~9 steps... which to me seems very doable.
https://www.instructables.com/How-to-start-your-car-from-a-cell-phone-via-GSM-re/

I'm just not looking to spend a ton of $$$ because I spent ~$200 for the automatic start already... I've seen some very simple relays on websites like Aliexpress.com and Wish.com that go for ~$20-30, but I'm not sure what their capabilities are (or even how to tell because I'm not very certain as to what I'd be looking for, etc.)

Would someone maybe direct me to the actual "components" I'd need in terms of the relay/switch? I also would be curious about how you'd "program" these devices... I have seen there are some that require only a particular string to be sent via text message to program the whitelisted numbers, timers, etc.

TIA, guys!