Can't help on suggesting someone to look at the car but obviously look for rust as they are no different from other cars of the mid 50s in that respect. The floor, rocker panels, space behind the stainless surround above the headlights and in the flat panel below the trunk lid as well as a channel at the rear of the trunk floor in front of the flat panel are areas prone to rust in 55-6 Packards.
55 was the first year of the V8 and early engines had oiling issues leading to noisy lifters. Those known causes should have all been taken care of back in the day but just be aware that since Packard essentially went away there could be some items that were needed but never actually changed. This is particularly true if a Packard dealer or even a later Stude dealer that was thrown into Packards was not the primary repair source that the car was taken to when still young.
During the post S-P years engine wear and particularly the oil pump capacity was suspected of causing many of the issues but there has not been conclusive proof pointing to one known object. At any rate, a conversion kit was developed a few years ago to install an Olds pump in place of the original which seems to be a proven mod. Although you do give up the crankcase mounted aux vacuum pump for the wipers when installing the Olds pump the aux vacuum source can be replaced by a dual action fuel pump so not a big deal other than authenticity for those that would know the difference. Parts for engine mods that might not have been done in early years are available and the combination of the two seems to have alleviated the lifter issues.
Probably the biggest issue with 55s was the Twin Ultramatic transmission. That was also essentially a new and barely tested item. Packard reworked the valve body on the original no shift single speed plus torque converter Ultramatic to allow the transmission to either work like the original or there was a second mode where the operator could have an actual shift between low and high range to provide better acceleration. That valve change along with the Ultramatic being originally designed to go behind a low horsepower engine but suddenly being fastened to a high horsepower V8 proved to be a weak spot and probably the major reason many 55 Packards developed a bad rep. A significant number of changes were made during the 55 year and more were made for 56 TUs. Some of the 56 changes could be retrofitted to 55s. Most of the original issues were resolved but again the car might not have received all the changes. Just be aware that the transmission is a weak spot but driven with decorum and not subjected to a race track mentality they will provide decent service. Not many trans shops will touch them today which is for the best since they are somewhat different and unlike other trans of the day. A mechanic not familiar with the operation or where to look for issues can cause significant and expensive damage but quality people are still available. Rebuilds are not cheap though and the places that do work on them are few.
The other major new feature for 55 was the Torsion Level suspension. That has proven overall to be very reliable but like other things approaching 70 years old things happen. Electrical switches are old so cause most issues but are still available or have been reworked to modern standards. Biggest issue with 55s was all the electrical parts were under the car and subjected to moisture or being damaged by road debris. Mechanically, aside from rubber bushings, there is not too much to go wrong with the hard parts unless something electrical failed and caused damage by allowing a link or bar to travel too far. Some of the parts are different for 56 so not a direct interchange on a few them but again like electrical, most hard parts are still available from Kanter or Max Merritt.
There is a 55 owners manual as well as most factory sales and service info which you can freely download at www.packardinfo.com
if you would like to familiarize yourself a bit more with Packard.