Jen, it is possible to get half decent shots with a dslr but in the end you will want to go for a webcam or DMK as it will just make life easier. The PST doesn't need to be modded for this.
However if you use a DSLR there are a few things that'll make life easier and you should get a usable image.
Firstly I use a Hyperion Zoom EP as it has a t-ring attatchment and takes away the need for a barlow. There are other zooms that are the same so a Hyperion is not essential. I guess a zoom isn't essential either as you apply the same principal but you might not get the full disc.
Secondly using a camera capture software like APT or canons own software helps immensely with focussing, which is one of the hardest parts.
I found using the x10 zoom on the cameras live view .helps a lot with focus and if you can zoom in on a sunspot all the better.
You will need to take two images, one overexposed to get the proms and one much darker to pick up the surface detail.
Try an exposure time of 1/500 at iso 100 or 200 for the surface detail and 1/25 from the proms. They are just starting points but you can adjust the settings once you get it sorted.
To make a recognisable Ha picture out of it processing is where it all happens.
You had the right idea changing it to mono but you also have to isolate the red channel as that is the one that picks up most of the Ha. So open up the image, turn it to greyscale and do away with the blue and green channels and just work with the red.
You can also open up the pic of the surface detail in Registax and apply wavelets and that may help with the detail.
Once you combine it with the overexposed image for the proms(generally cut and past not a stack) then you can change the image back from greyscale to an RGB image and play with the colour balance until you get the right colour you are after.
Now this is all a terrible faff but it is all possible and if you don't have anything else at hand then why not try it, however you soon end up with a DMK as it makes everything not only easier but better.
Here is a early pic of mine using a 450D, I had awful focus issues that in the end caused me to stop using this method but others have been far more successful than I was.
I hope all that makes some kind of sense, if not I can try and elaborate more.
cause thats what i was going to use earlier hahahaha 
one of them i changed to monochrome 
