Use the camera as is... It's quite capable in most situations. I used a pair of 30Ds for several years and got a lot of great shots with them. I've upgraded to newer models twice, primarily for better high ISO/low light performance and for a bit more enlargeability/cropability. But if light is reasonable (up to ISO 800... maybe 1600 with some extra work), you "fill the viewfinder" and use good lenses on 30D, they are very capable cameras.
Internet sizes and resolutions don't do them justice, but I've printed this 30D image 11x14 and 12x18...
...And this 30D image has been printed up to 8x10, so far...
...And this 30D image has been printed 8x10 and 11x14:
Other 30D images I've printed as large as 16x24".
The lenses you use on it will make more difference than the camera.
Enjoy your new (to you) camera!