I think that is the Model 99H; they were made in .22 HP, .25-35, .30-30 and .303 Savage, with a 20" lightweight barrel and straight pistol grip, made from 1905 to 1915.
The marking on the carrier spindle indicates the original caliber (if the spindle has not been altered). Those spindles are marked because they are very specific to the caliber, and I am not sure a .22 HP spindle will work with .30-30, even if you put in the .30-30 barrel. Is the rifle a take down type with the spare barrel only having to be locked into place, or would the extra barrel have to be screwed in using a barrel vise and wrench?
Value runs from around $500 in 60% condition up to $1400 or more if NIB. With a homemade buttstock, yours would be at the lower end or below, unless the rest of the rifle is in top condition - unlikely as that might be. I am not sure how much the extra barrel would add; it depends partly on the answer to the question about a takedown model.