[Closed] Replacing a Fox RP23 XV Boost valve shock

I'm riding a 2010 Orange ST4 Pro currently fitted with the above shock (2010 vintage as well). The shock is due a service, not least because the pro-pedal is now totally defunct. As far as I can find out, the pro-pedal failure is fairly common and requires a nitrogen recharge to resolve which rules out home servicing. Part of me is reluctant to be spending £100 a time servicing a 6 year old shock if there are alternatives out there.

A quick browse on eBay shows up a couple of Rock Shox monarchs in the right eye to eye lengths 190/51 vs the original 190/50mm at around the £150 mark - an RT Debonair 2015 new unused model and a 2016 boxed new RL.

Being honest, I have no real idea how these would compare to the original in terms of performance - my knowledge ends at working out they are the right length! The original is quite bottomless feeling with the linkage set up on the frame, I guess the Debonair would be more comparable with the high volume of the rp23?

So, any thoughts on the best route to take? Is the monarch a more straightforward service (ie home mechanic possible)? Are they comparable in performance with 6year old fox technology? Any other suggestions? Riding style means I really would like to keep a lock out option (or an effective pro-pedal that lasts without £100 servicing every 6 months!).