Welcome to the boards! You certainly came to the right place.
Photos would really help out. See:
How to post photosFrom your description, it sounds like you have a Russian SKS that was refurbed prior to import to the US. After import, it appears that the receiver cover was swapped out with a commercial scope mount cover. W/o the original cover and a pristine stock, I'd be wary of calling it a '1951' SKS despite what the markings might say until you can compare the feature sets to a '51 model. A gun like this should have a square ear solid bayo lug, early style receiver, 45° gas block, and a tabbed gas tube takedown lever.
A bubba'd gun like this will never be able to keep up in value with a pristine as-issued specimen or possibly even a nice clean refurbished gun. As the gun belonged to your uncle, it does have sentimental value to you and you can shoot it w/o having to worry about it.
As for learning additional information about Russian SKS45s, you can always start with the
Russian SKS FAQ. Additionally, the
www.SKSguide.com Russian section has a bit of information in it, though it is still mainly under construction. If you have any questions, post them or even type them into the shoutcast chat box at the top of the sks-files.com home page and I'm sure you'll get a knowledgable response from the good people here.