eBay "forced" the majority of sellers to use PayPal and ONLY PayPal a while back on most categories. Some big ticket items are excluded (cars, boats, planes, etc..) where the transactions occur face2face.
To the OP I would recommend adding SIGNATURE CONFIRMATION when you ship. Last year I shipped ~ 500 items via USPS Priority Mail. I mostly sell
LEGO related items on eBay. In any case I had 3 cases last year in which charge backs were done becuase the buyer claimed I never delivered the items. Got burned on the first one (before I was using SIGNATURE CONFIRMATION) as I only had proof via CONFIRMATION DELIVERY & PayPal made the determination that while the item was "delivered" it did not get to the actual buyer or his representative. Learned my lesson on that one lost the money on that one. So now I pay for the SIGNATURE CONFIRMATION and it has worked nicely. Has 2 more cases where buyer try to do a charge back and this time PayPal afetr me sending them the paperwork with the signature denied the buyer's request and banned both of them!
Also don't forget about taxes. Uncle sam is going to want his cut of your profit at the end of the year. Put aside about 25% of your profit for this. Plus I would recommend NOT allwoing sales within your home state. Else you will have to collect and send your state it's taxes as well. It's not that hard but then your local county/city may want it's share ofthe taxes and the county/city may impose "biz" permits cause you have a "biz" even if it's in your home. Then the city/town can fine you for havine a home biz in a residential zone.

It's a MESS and unless you are going to be bring in big time $$$ (100K+) I would not go this route yet. If you get bigger then incorporate and tell with all these additional taxes.
To help you out get some type of tracking software (Quicksbooks is great) to track your sales and expenses. Quickbooks (what I use) also has tax reports that you can use come tax time. It may seem like a lot but slowly but surely you will get there. Good luck.
Pm or eMail me if you have more questions.