Eric, I'll jump in with my 2-cents, subject to the others giving info.

I was in Paco's at least several different trips to Reno. It fronted on Virginia St., just south of the Reno Arch. A rather small place with some live tables, some slots, a bar, and possibly a small diner-style coffee shop (not sure on that). But ...
Paco's had an escalator in back that took you up to an enclosed sky-bridge that crossed over Sierra Street (runs parallel to Virginia St., but 1 block to the West). Go across the sky-bridge, down the opposite escalator, and you're in Flamingo Hilton.

Yes, Flamingo Hilton owned Paco's at that time, and used it as a funnel for customers to get from Virginia Street (populated with most of the downtown casinos (Harold's Club, Harrah's, etc.) as an entrance to the Flamingo Hilton, without crossing streets ... or in cold weather, you could stay warm!

The F.H. operated Paco's with a different name (and perhaps a different gaming license too?) since they bought it from a prior operation. Also, it had different look, different (lower) limits, and no hotel, as contrasted to the more elaborate Flamingo Hilton-Reno.

I would need to check my Reno gaming history more thoroughly on this next point, but it's my recollection that originally, Reno city fathers (city council?) wanted to limit downtown gambling joints to just Virginia Street, in the handful of blocks south of the Reno Arch. But when Del Webb bought the real estate on Sierra Street, 1 block away from Virginia Street, he circumvented the zoning for his new Del Webb's Sahara Reno casino by building the sky-bridge and joining it to the back of the casino which would later become Paco's. Over time, the zoning restrictions were dropped and other casinos opened all around town.

Hope that helps clear it up a bit.

(BTW, in looking at today's Google map of this area of downtown Reno, it appears that the sky-bridge doesn't exist any more, nor do most of the casinos that were on Virginia Street south of the Arch. Too bad; kinda sad. )