Jokes, I read the whole thing.
I would say before thinking about new injectors you should look at getting those few issues sorted first. Get yourself a replacement thermo fan, get that sensor and that plug sorted. Then should service the beast, oil, filters, check belts etc. Then get a comp test done, will give an indication as to the condition of the engine, no need to buy a new one if the current one is okay, the RB25s are pretty robust. Then you can start looking at exhaust and a little more boost as well as getting those suspension niggles sorted and go from there, will be able to boost it a safely with the stock turbo, injectors better exhaust. There is a large mods market for the R33, both new and used, so yeah, should be able to get some nice parts cheap.
Send us some picks of that plug and the sensor and the intercooler situation.