Don't really know about converting it to look like an A class, but I would say it would be a lot of work! I don't think the overall dimensions are correct, plus it's a Bo-Bo.
The Heljans are lovely runners on DC and DCC. By the way, if the model has the older brass wheels replace them, they get dirty very quickly and will break your heart on DCC!
Fitting them with sound involves a little work though, here's a good video....
Personally, I would leave it as is and install a Class 33 sound chip! They're a lovely model and it would be a shame to hack it up.