I did it a couple of years ago on my 69 FHC. Took a week. It wasn't so bad a job. Take loads of pictures.
It is serialised in the knowledge base on this forum, here is my small contribution though.
Most of the bits came from RS Smith 01270 780954 and these came to about £1,660 including the dash panels, glove box liner, RHD steering rack, VAT, Throttle pedal assembly + linkage, Wipe arms, brake and clutch pedals, steering column cover, bulkhead cover panels. I had to buy some service items as well.
I would buy the pre-covered dash panels, as pressing the leatherette into the correct curve prior around the choke and heater lever recess can be difficult.
I would change the steering rack rubber mounts for upgraded poly bush items (£80 ish)
viewtopic.php?f=3&t=11960&hilit=lhd
Most of it explains itself as you go along, So I wont go into to much detail, however the running order if I had to do it again would be( with the bonnet on).
Disconnect the battery.
Unbolt the 2 steering column uj's. Be vary careful not to round the allen key pinch bolts. I Replaced these two items the new UJs which used 13mm bolts instead. The UJs were cheap.
Remove the steering wheel (expensive), shroud (expensive to replace) and indicator switch (expensive) and upper column making notes of the ignition switch wiring. I scratched to colors with a scribe, onto the back of the switch, which has helped me a few times since! You have to be a bit careful with the ignition switch wiring as when the battery is connected it is un-fused and live!
Play in the upper column (steering wheel moving up and down) on my car was removed by replacing a broken wavy washer held with shims and a circlip at the base. Not sure if your car is the same as yours is an S1, mine is an S2.
Unbolt and remove the track rod ends using a ball joint splitter. I replaced the ball joints.
Unbolt the slightly tricky bolts and fail safe bolts on the rack to frame, passing through the rubber mounts. Take some pictures on you phone.
Each rack mount has 2 fail-safe bolts. 2 on each side. The drivers side bolts compress a crush tube directly onto the frame, without gripping the rack, allowing some movement in the rack left to right when you turn the wheel. When you re attach the new rack, these crush tubes will need to be transferred to the other side.
From memory the other side fail safe bolts squeeze washers. I replaced all the nuts bolts with cadmium plated ones and nylocs.
My wiring loom was in good condition. At this stage my mobile electrician had shortened the lhs wiring loom and re-terminated it for rhd. This took 2/3 days and I paid him £300. The loom runs from right to left so it is easy ish.
The pedal box swap was straightforward, new blanking plates bolted in. New masters for clutch and brake fitted and temporary vacuum hose to the servo on the S2, as the metal pipe in the bulkhead is not fitted to LHD cars.
Throttle linkage was easy to fit, difficult to perfect! The secret was to make sure the throttle pedal does not stretch the linkage when you boot it. Otherwise you end up with a 1,500 rpm idle speed a few miles up the road, making M25 driving hell.
I unbolted the two rhd and lhd panels, swapped the gauges over. You might like to consider changing the dreaded heater pipes in the bulkhead void at this stage. Nasty job but worth it.
Make sure all the levers work prior to refitting the new rhd panels. Pass the cables through the bulkhead first. It is difficult to adjust the heater controls and the choke levers, especially with the screen in place after you have fitted the panels. Reconnect heater pipes and glove box lining.
The center gauges I left alone. I fitted a new dash pad using a heat gun and spray adhesive. Your dash pad might have an extension as it is a +2.
I took the opportunity to unpin (drill out) the steering column ignition lock and I swapped the position with the indicator, that was straightforward on the S2 column. Not sure if your column is the same.
Watch the new fiberglass and rubber column gator. They can squeak if you dont adjust them.
I had to remove the lower radiator hose to swap out the racks, and get the tracking re done!
About a weeks work I would guess.