The standard ecu can be chipped, that is to say simply open lid remove one chip replace with the new one, plus any setting that are given for the chip, such as boost fuel pressure plugs etc.
If you are going to be fairly settled on this engine spec then that would be your cheapest option, but if the ecu is from the 3 door also, then it is a L1 version, so not the best will do the job and nothing more, if wanting anti lag, launch control etc then it will need to be a L8(4wd sierra), or P8(early big turbo escort cossie).
MSD has all the above chips etc, but it would be money very well spent getting a live set up, this is where they take your actual car, and tune/map it it self, you can get so much more out of it safely that way.
The other option is aftermarket ecu, there are laods to choose from, with very varying prices, a lot have features you may not want or need, so don't pay over the odds for one, you also want to consider who is going to map it, no point travelling the length of the uk if you don't have to, so see who's local to you that is good, and have a chat, people have thier own favouorites for various reasons, and of course a lot boils down to budget!!
tabetha