A new injector costs you about $30, plus another $5 or $6 for the seat and the seal. The seat you can most likely skip, the seal is a must. However, identifying the injector is a pain, and me being a former airplane owner and a current pilot, I don't like to take risks - i.e. if one went, then others might go too, so I replaced them all. If you do that, you might budget replacing any air hoses that attach to the injectors (I don't know what kind of car you have, I have a 89 560SEL, and it has two hoses at about $12 a piece that fed into the injector holders.) If you DO do all the injectors, replace the holders as well.
The accumulator might be a first try - you can test for it (search oher posts here). If it fails the test, you got your problem, and it's not bad replacing it - it's just as easy as doing a fuel filter (at least on my car).
I DON'T think your problem is in the ignition or any of the other computerized systems - if it works fine but has some trouble starting warm, I'd bet it's a leakdown, and if it's a bit rough I suspect it's an injector causing the roughness and the leakdown.
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)