Whoever told you that about the steering wheel is wrong. Although a 300 wheel can use your 190 airbag and will fit your car, the 190 16V has a smaller diameter wheel than the 190 or 300 series. Although the 16V wheel is still big, changing to a 300 wheel will be even larger. The only way you are going to get a smaller steering wheel and keep the airbag is to buy a new airbag too. This is because you could get a smaller wheel, say a C43, but your airbag is too big to fit in that wheel. Airbags have gotten much smaller due to US law changes. With the airbag you have the 16V wheel is the smallest you will be able to get. I am just canning the airbag and getting a MOMO, besides, my airbag expires in two years anyway. You are suppose to replace them every 15 years, and I'm not paying $2,000 for a new one.
I am not familiar with either of the shops you have mentioned. Are you looking to rebuild to stock spec? Or are you looking to get more out of the engine. Bekkers 2.6-16 stroker is a very econimical way to go if you are looking for more power.
MBCA, PCA, BMWCCA & SCCA* member
86 190 2.3-16
83 944 ITS Racer