I have a 2018 R5, and had to replace the 24 mm BB (for the Ultegra crank) with a GXP crank so I could use my Quarq.
I believe all we used was a standard 48.5 mm x 16 notch BB wrench. Pretty much every shop should have one. The existing BB I believe is made by wheels manufacturing (link
), and each side screws into each other in the middle. So all we did we loosen the drive side about 75% of the way (still threaded 25%)...then used a rubber mallet to pound the drive side which in turn pushed the non drive side out of the BB shell. Then we unscrewed the drive side out the remaining 25% and now both sides were removed. Of course, this action could ruin the existing 24 mm BB (but I didn't care), so maybe that's why your LBS says you need a special tool. The may have the intention of fully extracting the non drive side using the 48.5x16 wrench, then use a special tool to push out the non drive side without pounding on the bearings.