21 old Driver need some help

Hello guys my name is Gary, 21. I just become owner couple weeks ago, so right now im trying to find some parts for my truck which is a Freightliner Century 2006. I live in California, so basicly im newbie in the business i would like to ask to the experienced drivers. Where can i find a good shop to buy some parts( like refrigerator, power supply, digital gauges (looking so bad), etc.) I love tunning in car so im trying to keep my truck nice. Thx for ur help floks and have a good 1, drive safe. GARY