OK, I'm a bit OCD and DIY, but I just don't trust assembly of things like that to the local store. The instructions are typically confusing, and doing it right can make a difference to how well it works, or how long it stays together. And when something comes apart because it wasn't put together correctly, that can often lead to damage of other parts. They often just pick a high school stock boy to do the job.
As an example - the movers took apart and put together our old bed frame when we moved. A few weeks later, I realized that one of the insert threaded metal dowels was missing, and the guy just put the bolt in without the fastener. Longer term, that joint would come apart and as it gets loose, the leverage builds up on it and it can get pretty seriously damaged. I picked up a replacement fastener at the hardware store, and checked the whole thing.
-ERD50