My first question is what do you want to image? If you are wanted to image at the equivalent magnification of that scope with a 4mm eyepiece you are in the neighborhood of 300X. So problem number 1 is that tracking might keep the object reasonably centered but a Dob mount is an alt-az system. The scope does not rotate with the sky so you have to keep exposures very short to avoid blurring from field rotation. If you are trying to image planets, they are reasonably bright and you can stack multiple very short exposures and possibly get a result. DSO's generally require hours of data(multiple longer exposures stacked), with autoguiding, on an equatorial mount. It is a challenging just to learn at a 400-500mm focal length of an 80 mm refractor with a good mount. To attempt to learn AP on a scope above a 1000mm is only something attempted by masochists!!!
Another problem is using a Barlow. It does change the focal length to increase magnification, but crucially it also increases the focal ratio by the square of the Barlow's power. I think a 3X barlow would increase your focal ratio 9 times! Someone smarter than me can tell you the math but that creates a massively "slow" focal ratio. By "slow" we mean that focal ratio is critical to how much exposure time is required. I think an f4 scope gathers light 4 times faster than an f6 scope of the same diameter. You could try that Barlow on a bright planet but pretty much everything will require all night vigils for a week to see anything else. I don't know, I never tried it. But I think it could be brutal.
You can play with an EOS Rebel and a Dob for planets. But if AP really intrigues you, think good equatorial mount with a small fast(f4-f6) scope. Or if money is a big challenge, think about getting a camera tracker to start with.