RCA VMT25S

Say what you will about consoles but I am quite happy with my recent purchase fueled by fond memories of listening to my grandma's console as a kid.
That being said, the first thing I learned was that I know very little about phonographs.
I know this model was from 1966 and it's in really excellent condition, but other than that I can't seem to find any info on it. Some of you seem to be able to gleen information from the model numbers and that would be helpful.
I would like to make sure I'm properly caring for it. Would you suggest that I open the back and clean it somehow? (a general dusting)
The thing sounds great, my only complaint is that the bass dial seems touchy. LITERALLY. When I touch it, it gets a surging sound and I can't really put the dial at anything higher than 2 without sounding really distorted. It doesn't appear that any of the other dials do this. I'm sure the old lady who owned it never touched those dials when she was playing her polkas.
Not knowing anything about these things....how hard is it to just put a really good pair of speakers in them? There is an external speaker jack...what would that have been for? How much would sound improve with a new needle? the needle has been replaced once that the previous owner knew of. Are there things that should be lubed/cleaned in order to keep this in good working condition? Any help would be appreciated!

As an expert servicer/restorer of RCA consoles, (among other brands) I will tell you that after decades of neglect, it'll need proper servicing if it's to continue functioning.

Forget about any internal "dusting" - best done by a servicer, to prevent accidentally damaging anything inside.
The speakers in these RCA's sound great if they havn't been messed with.
I've rarely had to replace them.
The sound issue you're having is caused by deteriorated components in the radio chassis - something best done by a servicer.
So that being said - avoid using it until the proper service has been done, to prevent further issues - costing more to fix.

The record changer will need a good overhauling - they all do, remember decades of age and neglect have taken place silently.
Old grease has now turned to glue, and oil has dried up - using these without an "oil change" is like driving a car that hasn't had service in decades. - not smart.

I recently serviced the electronics and changer out of an RCA, for a guy in Florida - he shipped me up the "guts" - and as usual, I had to work my magic on them, but now they're gonna sing pretty for decades to come.
And I like to keep these things running for people, to keep them from landing up in some landfill or dumpster - they just sound so good!

I hope this helps.

-Matt