I’m not clear what you mean when you say “0.3 security”. If you are talking about the system, that is low sec and can be quite dangerous if you don’t know what you are doing. But there is no issue with you leaving a ship docked in such a system. In time you will end up with assets scattered all over Eve as you move around.
If you’re talking about your own personal security rating, 0.3 is sound.
Onto the problem, as reply one stated, you can leave your current ship in your ‘home’ station and just appear in you pod and then fly to the station where your new purchase is to pick it up.
However, if you are going into low sec, it is best to wrap your pod in a cheap ship, that you can abandon when you get there. The ideal ship is a shuttle, these cost around 20K isk (be careful of overpriced scams), but make sure you are buying it from either your home station or a high sec station that you can reach or you will have the same problem all over again. The advantages the shuttle gives over a pod is faster align time, warp speed, slow boat speed and general agility. Plus it has to be destroyed first, before they can get your pod. In addition the packaged size of a shuttle is only 500m and it will fit in a lot of ships cargo bays if you repackage it so you don’t have to actually dispose of it. If it doesn’t fit in the cargo bay, you might be able to reprocess and bring out the valuable minerals instead. Alternatively you can leave it on a sales order or just scrap it, but it doesn’t hurt to leave shuttles scattered about low sec systems, one day you might lose your ship near it and it will come in useful.
If you can’t get hold of a shuttle easily, use a noob ship. To get one if you don’t already have one available, simply undock in your pod and dock in another station where you currently have no ships. A noobship will be spawned for you. Note you will have to open your hanger window and board it. Noobships aren’t as fast or agile as shuttles, but do have a much larger cargohold if you need to carry some fittings for your other ship. But if it is in low sec, only carry cheap fittings that will assist in the movement of that ship, such as prop and agility mods, maybe a damage control, and fit it up properly when you get back to high sec. Don’t take an expensive implant laden pod into low sec if you don’t know what you are doing.
Certain low sec systems are regularly camped, typically ones that are choke points from high sec. Tama, Rancer, Amamake, Old Man Star and Huola in particular are systems you should avoid if you don’t know what you are doing.