Not a comprehensive list but here are some highlights:
G cars had the ventilation ducts removed and replaced with underseat heaters right behind the grilles, blank panels in the ceiling where the ducts used to be, along with overhauls of trucks, motors etc. plus bodywork and repainting. interior (doors, various trim) and exterior, floor covering replaced. G car overhaul lasted from 1967-73, didn't originally include the ventilation duct removal which was added later.
M cars had the first overhaul in 1974-75 where the door control buttons in the cab were moved from the rear wall to under the cab window, otherwise, similar to G cars except for exterior painting. M cars second overhaul, 1986-88ish, had the cab enlarged and equipment overhauls, plus painting of the interior of platform and intercar doors. Originally they were brushed aluminum, some had the bottom half of the doors painted, some had all the doors painted.
H-1 cars had overhauls ongoing due to heavy use but not a specific program for them until early 1990s after motor mount problems - car ends and roofs painted, equipment overhauls. plus door interiors repainted.
H-2s and H-4s - ongoing overhauls, but nothing really noticeable to the passengers. H-2 conversion of six cars to chopper control was done at Greenwood in 1973, and the removal of the same equipment in 1984 would have been done at Greenwood. H-4s had a late overhaul around 2001 where just under half got a more thorough refurb. Those could be identified by the grey painted ends.
H-5s had a rebuild in the late 1990s - door frame corrosion repaired, repainting of car ends and door interiors, equipment overhauls. Hard to tell with a/c, it still smelled like a musty basement. H-5s repainting original black ends to silver and then repaints were done at Greenwood.
H-6s - similar to H-5s, plus various replacements of inferior original equipment as approved. H-6s also had all trucks replaced at some point around 2000 maybe.
Stuff like the fleet number panels, decals in the door windows, Staff door decals, etc, were probably done at the carhouse, while stanchion installation and replacement were likely done at Greenwood. Any other comprehensive equipment replacement that would be done on the whole fleet was probably done at Greenwood as one could always see cars of all types parked outside the shops.