It is all good. Just have fun with it.
I was in the same boat late last year. Wanted to get into the larger scale RC but not much to choose from that was affordable unless it was used. HPI did not have anything. Losi has stuff but expensive to start out with.
Detroit Performance RC, DDM Racing are places I frequently use.
Other resources like Rovan RC, King Motor RC, (Fearless RC same as Rovan and Km). Integy and TIT-Racing. Ebay and other places but they are mostly Chinese resources. Rovan will have more parts or upgrade kits than King Motor. Some of the King Motor parts may be of better quality but that all depends on what it is. However, there may be some parts that will not fit. TIT-Racing does have some common parts but once it a blue moon it will not fit. Bought a fuel tank and it did not fit. Bummer. Other parts I have ordered from TIT-racing were good. I would recommend before you buy parts including upgrades to compare to Detroit Performance RC and DDM.
Taylor RC is also a good resource, since I live in the States, I get the Taylor / RCMAX parts from Detroit Performance.
I did upgrade my King Motor considerably before I slammed it into a wall. After that, I used Detroit Performance RC and DDM racing to source parts to build my own 5B Baja. A few parts from Rovan were also used. Once you have that general idea how to build one, it is not difficult to do so.