Bachmann Heavywieght Passenger car repair & mods?

[Opalman]

Hello,
I’m fairly new to the hobby having collected thousands of dollars of
rolling stock and diesel locos only to have them stolen in a move
before I could even begin building a layout. Now 14 years later I’m
starting over, acquiring pieces on-line and on eBay. I just received a
set of nine Bachmann spectrum “heavyweight” passenger cars in the PRR
road: (5) coaches, (1) baggage car, (1) observation car and (2) diner
cars. The cars are pretty nice and have been weathered slightly (good
workmanship), but the interiors were not painted. Several of the
couplers need work. I have ordered rubber diaphragm kits for all. I
need help! I have not a clue regarding how to gently remove shells.
Also I want to know what my best lighting options are; the rearmost
truck on each car has an elec. Pickup (brush) leaf...will the
recommended lighting work with these stainless steel leafs & DCC?
Since several of the couplers have issues I thought I’d install all
new, which should I purchase? What trucks and wheelsets are best
quality and prototypical?
Three of the coaches have duplicate road numbers. Is it possible to
fix this be re-decaling those duplicates. If so what should I use to
remove the original deals?
Your advice is very highly appreciated.
Regards,
Tom