Sounds like you're using manual mode. Absolutely nothing wrong with it, but aperture priority or shutter speed priority are probably easier to get your head around the exposure triangle (aperture + shutter speed + ISO) before moving on to manual.
In your example, I think your ISO needs adjusting. If it's blurry, you've selected too low a shutter speed. I assume you've already selected the widest aperture, so you need to increase the ISO which would allow you to select a faster shutter speed while still having it bright. If it's too dark, your shutter speed is too fast and there isn't enough light coming in, so you again you need to increase the ISO. Unfortunately your camera is pretty old and the sensor is kinda naff (I used to have an E-P1), so anything above say ISO 1600 will start to look bad.
As for lens recommendations, M4/3 has a lot of great prime lenses in the selection. Cheap zoom lenses, not so much. I'm probably forgetting some, but the only other zoom lenses which would actually be an upgrade would be the Panasonic 12-35mm, Olympus 12-40mm and Panasonic 7-14mm (or Olympus 9-18mm), and you're looking at 300-500 for each, even second hand.
Prime lenses on the other hand, you have the Panasonic 14mm which can be had for under £100, Panasonic 25mm f/1.4 for around £200-£250 I believe, Olympus 17mm f/2.8 or f/1.8 for around £200 (the former quite a bit cheaper), Olympus 45mm for around £150...
There is also the option of renting lenses for the trip too, so you could get one of those nice zoom lenses for quite a bit less than it would be to purchase...