I loved my almost stock GN. Set a budget then go from there. Bone stock it should run 13.8-14.2 at 96-98 mph depending on weight and conditions, tires, track etc.
TT chip
Good 340 style walbro pump
Hotwire the fuel pump
Change Fuel filter
Adj Fuel Press regulator (chip requires it)
Mech boost gauge
Scanmaster in glovebox or G one in dual pod
Dual or trip Gauge pod that sticks to right of dash, not A pillar
Gut the stock cat
Adjustable wastegate actuator - you can take it off, cut it, thread it and make it adjustable easy enough
Valve springs if they are original, you'll float them.
Verify TPS and all sensors in spec via scanmaster.
New Denso O2 sensor.
Run it like that on pump gas, should go 13.0's at 103-104 through the stock airbox.
I too purchased a bone stock Turbo T last year and followed the above suggestions. The important this is to get the car running properly before you start to modify. There is a lot of information in this site. Be patient and go through as much as you can. I would start here:
http://www.turbobuick.com/threads/info-for-new-turbo-regal-owners.380856/
Below is what I did and last month I ran a 13.3 at 100 mph.
-transmission fluid and filter change
-rear end fluid change with Redline 75W90
-Brake fluid flush
-oil change with AC Delco PF 52 Filter and ZDD Plus Additive
-Scanmaster
-boost gauge
-AC Delco R43TS Spark Plugs
- 160 Degree Thermostat with Kirban Stainless housing
- PVC valve and grommet
-check all belts and hose etc.
-Racetonix Hotwire Kit
-Test Pipe
-RJC Power Plate (clean the doghouse and throttle body at the same time)
-Metco Test-n-Tune Fuel pressure gauge kit
-Kirban adjustable fuel pressure regulator
-AC Delco Fuel Filter
-RJC Racing Plug Wires
-RJC Racing 3" Exhaust (expensive but it will out live me)
-Kirban Mass Air pipe
-9" k&N Filter
-Turbo Tweak Chip
-Racetronix 255 Fuel Pump
-Passenger side air bag
-Kirban Adjustable Wastegate Actuator
-Mickey Thompson ET Streets 255-60-15
-Denso o2 Sensor
I only drive the car a 1,000 miles a year so I try to use unleaded 100 octane as much as I can. Again I am no expert on these cars but the above has worked for me and I am happy with the results. I can take my daughter to get ice cream and go out on date nights with the wife and not get embarrassed by some kid in an EVO. The main thing is to have fun and enjoy the car!