If you have a 240V mechanical timer already you can wire in a Intermatic PF1102 freeze guard to work with it, wiring is about as difficult as wiring a 2 way light switch, if you need an electrician somewhat depends on your skills, local regulations, etc. These units typically sell for around $150 or so online, and about double that from pool supply places. I would put typical installation time if done right by an electrical professional at 30-45 minutes max, pdf instruction manual is available online if you want to look for yourself. If you have a pool automation system already and not just a basic mechanical timer, then many of them already support freeze protection, but you may need to add another temperature sensor for $30 - $40.
Ike
p.s. from a price / ease standpoint it might be easier to change out to a unit with an integrated timer, as they don't cost much more. Such as the PF1102T or PF1103T depending on size and voltage of your pump