Ask as many questions as you want... that's what the forum is here for.

Only C1 (10nF X2 type) is surplus. This PSU was part of a Fan Controller which used a Triac controlling the Fan. C1 was there for noise surpression and in your case can be removed.

C2 is either an X2 grade capacitor, or, any 400vDC rated Capacitor. Look for metalised polypropylene or metallised polyester. Typical manufacturers are Dachs-Kondel, Arcotronics, BC Components (Vishay), LCR and TruCap.

VDR1 (11v) is a safety component. My original design was going into Hospitals... if Zener D2 failed and there is negligable power consumption by the target circuit, the voltage at the junction of D3 and C3 would rise rapidly towards supply mains level destroying the Regulator and every low-voltage component (ie the PIC) downstream. The Zener is the weak spot... if it fails, basically everything is toast. That VDR is sufficient to keep the supply from rising much above 18v, still well within the parameters (30v) for the Regulator. My PIC had additional circuitry (two Resistors as a potential divider to an ADC pin) that detected that the Input DC supply to the Regulator Q1 had risen above 14v and flashed an LED to tell maintenance engineers that the unit is broke. Omit VDR1 at your risk.

PM me off-list if you have trouble finding suitable parts and I'll see what I can do.