I do my own oil changes on the three Subarus in my family.
The oil filters and drain plug crush washers can be found inexpensively on Amazon. I buy the 0-20 full synthetic oil at WalMart for much less than elsewhere.
If you are concerned about the crush washers, you can buy some and give one to the shop that changes your oil. Here's a link for the washers that are appropriate for a '13 2.0 Impreza, a '13 2.5 Outback and a '14 2.5 Forester.
10 Subaru Oil Drain Plug Crush Washer Gaskets 16mm
https://www.amazon.com/dp/B00BR3HMEQ..._rMvOwb2XJTV2T