Need advice, 90 suburban

[cfan10]

90 suburban with 5.7 tbi/700r4 transmission was in the shop for a transmission mount, now the truck acts as if it doesn’t want to pick up speed. Of course I took it back to the shop that did the work and now they’re trying to charge me to diagnose a problem it didn’t have until they starting “fixing it”.

The shop told me that it was probably the timing or something, but if I’m right timing will have some sort of indication (it starts right up every time, just idles slightly rougher at lights/stop signs) does it sound like a timing issue?
No timing tab on engine!

It also now takes a minute to engage into gear in order to move. Shifted perfect before. They claimed they used two gallons of the transmission fluid I brought in.

They actually changed the oil filter but did not change the oil.

Someone suggested it may be a bad fuel filter, but I didn’t have this problem before the shop.
Scary thing is the other day I took off out of an intersection and it actually died in the road, started right back up but scary as hell to say the least.
While driving it feels like it is a manual that needs to be shifted, if that makes sense.

I just need everything back to normal and running well, before Jan 2016 because it is my main transportation right now. Many thanks for your advice/experience. It is greatly appreciated.

Things I did recently:

Flywheel_9/2015
Starter
Drivebelt
PCV Valve
Air Filter
Fuel Filter_2/2015
Rotor
Distributor Cap
Spark Plug Wires
Spark Plugs
ICV Valve
TV Cable

A few other small things here and there, don’t have my list so I’m playing off of memory.
I hope I don't get anymore surprises from their "work"