Made the 300 mile drive home with no repeats of either issue. Before I left I checked and exercised all of the air vents and there was no reoccurance of the whistling sound. Didn't check the filters, but they ought to still be okay after 7,000 miles based on my previous experiences with them. On the transmission, I checked the fluid hot as soon as I got home and the level is midway between the high and low 80° marks. So assuming nothing else happens, I'll be changing the dust filters and doing a transmission service in 3000 miles. Will certainly look a little closer at the transmission fluid, pan and electrical connector when I do the ATF service.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles