Help with G scale RC?

[Snowman]

I have owned a G scale USA Trains locomotive for over 5 years now. Never had the track, we had big plans for a garden railway but that never materialised. But we've been talking about getting this project going again.
It's been so long since I've looked at G scale stuff, what I'd like to do is convert my locomotive to RC, with its own battery pack, so that we don't need to power the track and so I can run my loco totally independently.
Would this be possible? Looks like there'd be room inside for a battery pack. Is there anyone that makes this type of rc product, or anywhere I can find information on doing it myself?
I don't want to get dcc stuff or anything pricey/complicated like that, just control like you'd have for an rc truck.
Don't have any pics to show but will take some if anyone wants to see my SD40-2.