Upgraded bike confusion
I have a used 2007 Novara Randonee I bought a year or so ago that was upgraded by the previous owner and it had some minor shifting issues. I'm fairly new to bicycle maintenance but I'm pretty mechanically inclined and do all the work on my cars and motorcycle. I've learned a bit about bicycle maintenance but still have a lot to learn. I tuned the rear (9 speed) and its pretty good but could be a little better. The front (3X) is a real pain though and I haven't been able to get it to work smoothly which has caused me to just leave it on the middle chainring. Some parts need to be replaced such as the chainrings, chain, cables and possibly front derailleur.
My plan was to do some maintenance and hopefully fix the shifting issues but I'm having trouble finding a derailleur for what I believe is a Tiagra 4503 crankset. I saw most stuff now is 10 speed including Tiagra which might cause compatibility issues? It looks like it would be a lot easier to find parts if I upgraded to newer stuff but I'll need to see what's compatible. If I did have to replace multiple parts I'd consider swapping to a 2X for ease of maintenance and the fact I don't really need a 3X. FWIW, I mainly use the bicycle for fun and exercising but plan to do commuting on it as well and would like to go the cheaper route fixing it up. Any help or input is appreciated.