Great question, not a silly one at all...
Agree with the points above - any CMS has a bit of a learning curve especially if you're new to the concept, but having used quite a few CMS before I think ProcessWire (PW) is not overly demanding and easier than some of the best known systems; especially once you get past the basics. I only have pretty basic PHP skills but so far I've been doing fine with PW; as Ryan has pointed out elsewhere, the PW API is very friendly - so the complexities of PHP are hidden from you in most cases, to the extent that it's no more complicated than the proprietary template tagging systems used in other CMS. However, the advantage is that you're learning a universal language with transferable skills and lots of online and offline learning resources to help you out - plus further down the line you have the full power of PHP at your disposal if you really start growing your ideas.
PW doesn't have as many ready built modules at this stage but then I actually think this puts you in a better position further down the line since you will understand what you build and be able to maintain it yourself. If you go for a system with lots of 'plug and play' modules then often you run into issues later if these aren't compatible with the CMS when it gets upgraded, your client requests a tweak which you can't code yourself, or the module is abandoned by it's author at some point. ProcessWire is as much a framework for building things as a CMS - so the further you need to push it the more you will appreciate not being boxed in by someone else's ideas - which is often the case if you go for a lightweight CMS (easier to set up in the first instance but much more likely to impose limitations later on).
Well good luck and look forward to more questions