The "large locomotive parking area on the north side of Schlossbergstrasse" is still there although typically it is full of DB 185s and the odd-hired-in TRAXX to BLS. SBB Historic also use this yard for their loco test runs however there is now a large metal barrier between the running lines and yard, making viewing as you pass, difficult.
SBB stuff is usually only parked on the shed itself, although there were even DB 185s parked there last weekend.
"What has happened to the area around the model railroad club, the parking lot and the spot where the crocodile monument was"
Can you be more specific as to where these were ? Alongside the SBB Loco shed (away from the station) is now a building that belongs to SBB-Infrastruktur, not really visible from the station/running lines.