The Fleet Status site is:
https://sites.google.com/site/unitedfleetsite/

At the site, you can find information about the interior features, livery, etc., for every plane in United's fleet.

United Airlines Equipment (Aircraft) Codes (via JOSECONLSCREW28)- code refers to type and configuration but not IFE:

sCO
73Z - B737-700 Guam Configuration (12/30/84 Slimline)
73G - B737-700 Slimline (12/36/78 config)
73R - B737-700 Slimline, former GUM and former Copa (PDE)
73Y - B737-800 Slimline Config (16/54/96 config)
73U - B737-800 Guam Slimline Configuration (16/42/108 config)
73Q - B737-800 Slimline (16/54/96) with SFP (a/c 3519 and above 16/48/102) 3528 and up Sky Interior, 3532 and up Sky bins
73C - B737-900 Slimline (20/42/117 config)
73L - B737-900ER Slimline Config (3413-3442 & 3479: 20/42/117), (3443-3478: 20/39/120) (3479 Sky Interior and Space bins)
37X - 737-MAX9 Slimline 20/48/111)
75B - B757-200 Int'l Config (16/45/108)
75A - B757-300 (24/57/132 config) - obsolete with last 3 in mod
75E - B757-300 Slimline (24/57/156 config)
76P - B767-400ER (39/70/131 with Y crew mod)
78V - B787-8 (36/70/113 config)
78Z - B787-9 (48/88/116 config)
77Y - B777-200ER ("Version 2"/ 50/72/145 config)

sUA
19S - A319 version 1 (8/42/78 config)
19C - A319 version 2 (ex-CZ frames) (8/42/78 config)
20S - A320 version 1 (12/42/96 config)
20C - A320 version 2 (ex-CZ frames) (12/42/96 config)
37K - B737-900ER (20/39/120 a/c 3810-3810 ) (20/42/117 a/c 3811-3894 Sky - a/c 3895-3899 Space Bins)
75K - B757-200 (formerly known as "ps") (28/42/72 config)
76N - B767-300ER 3-cabin (6/26/71/80 config) - obsolete with last unit in mod
76C - B767-300ER 2-cabin non-Polaris (30/49/135 config)
76A - B767-300ER Polaris 2 class (30/46/138 config)
77G - B777-200 Domestic (Versions 3 & 4 / 28/102/234 config)
77J - B777-200ER 3-cabin (27xx Tail#'s) ("Version 1"/ 8/40/113/108 config)
77Q - B777-200ER 3-cabin (20xx & 28xx Tail #s) ("Version 1"/ 8/40/113/108 config)
77T - B777-300ER Polaris (60/86/156 config) - With Premium economy (60/24/46/156)
78U - B787-9 AC# 968-972

Here's what each of the facilities do historically:
HKG, heavy widebody maint and reconf (also heavy GUM 737 maint); 763 Polaris mods
XMN 772 Polaris mods, 777/787 heavy maint
LCQ, Airbus heavy and some medium heavy maint, Airbus Inductions and mods, 737NG reconfiguration
DLH, Airbus maintenance
MIA, 753 ISP, 763 main/WiFi, some 757 maint, 737NG reconfiguration and maintenance, Airbus maint.
HOU, 737 heavier maintenance, slimline seats, some shorter mod work
RFD, 752 scimitar winglets, 737NG reconfigurations, 753 slimlines
SAT 757 maint
SKF 39M final induction installations
ILN some 763 maint
VQQ some 763 maint
SFO, Airbus D checks, heavy 772 maint, 737NG C checks, other maint.
MCO, 737/757 maintenance, some mods.
IAH, light maint, slimlines on 73G
VCV, AMA and FTW for paint.
XMN, 772 maintenance
PVG, 788 modifications/WiFi
PEK, some widebody maint.
VCV, AMA, CWF, FTW paint
SEA, 77W, 739 new delivery induction, some 789s as well
DEN, IAD, 789 new delivery induction

Services ended at INT and MCN - Appears services suspended or ended at PEK