I did this a couple of weeks ago on my R65. The same spring died on me when breaking the bike in after piston rings change and clutch renovation...
When doing the clutch I removed the swingarm. Then when removing the gearbox to change the broken spring, I decided to try the method BMW advertise for post 1982 models : Leave the swingarm untouched but advance the engine in the frame. Lots easier !
You have to get an hydraulic jack or something equivalent, to put under the oil pan to get the engine weight.
First removve the airbox, battery and battery case, left foot rest , left carb. Disassemble the liaison between the mufflers and exhaust pipes. remove the clutch lever and cable and the actuation boot (beware there is a spring under it)
Remove the final drive boot and undo the four 12 sides screws.
Then whit the engine on the jack, remove the engines bolts on the frame and the two mounting studs. Using the exhaut pipes, pull the engine as far as it will go to the front.
Remove the bolting bits between the tranny and the engine case, pull the gearbox to the swingarm and using a pair of pliers, pull the clutch pin out of the clutch and into the gearbox. Once cleared, rotate the box to undo the neutral switch wires, and remove the box from the left.
It is as easy than that !
Assembling back is a walk in a park as you do not have to align the swingarm back and no need for the special machined 27 mm socket !