If..and its a big if....the HPFP on the front of the engine needs replacing are the special tools available that are shown in the WS manual?
Gear Locking tool. and guide pins etc...are they essential or can the pump be removed and replaced fairly easily without them
Access looks to be the biggest issue.

Im weighing up the pros and cons..do I keep going with this thing myself or pass it to a repair garage.

you can definitly do it without the guide pins and the gear locking tool but it will be a bigger hassel then with them. Access is a big issue yes you will need to remove a lot to get to it. Manly the Fan the intake piping and if a recall correctly lot of cooling pipes and electrical stuff.
it should be possibel but a lot of work and probably a lot of swearing 2010 Range Rover Vogue 3.6 TDV8

Just The usual extra tool box requirements then...😂
And a step ladder to get up to the bloody engine bay!

I am in a similar boat, but I haven't made up my mind yet (crank, no start).

Reading the WM it doesn't look too bad. I don't think the fan has to be removed. The critical part is lining up the woodruff key.

I think 4 RRS of this parish made an offer of a loan of some special tools but that was a while ago so may not be current and I wouldn't want to speak on his behalf. 2012 Vogue TDV8 in Aintree green over sand

I got myself an alternative for now.
Just bought a 2013 L320 HSE sport. It runs and stops....a great improvement