If the dealer won't let you run a patch through the bore and chamber, I would walk away from the deal. Pitting in the chamber is a much more serious thing than a rough bore. A pitted bore can still shoot well with jacketed bullets but a rough or pitted chamber brings with it extraction issues. The 35 Remington is not a high pressure round, that's good, but the 141 is a John Pederson design.It has no initial extraction. The bolt unlocks and there is no camming action to help with extraction, just a straight rearward pull. I don't think it would take much pitting or corrosion in the chamber to cause extraction problems.
I have no idea if that is a good price or not, I never see 141s around here. The .35 Remington is by far the best caliber the gun was chambered in. As an aside, that spiral magazine tube has a purpose. You can (not that anyone does with a .35 Remington) load spitzer type pointed bullets in the mag with complete safety. It does a very good job in keeping the bullet points from touching the primer of the round ahead. And it does a marvelous job of mashing and deforming said bullet points.....
One area of danger with these rifles, which you must check... I have a model 14 in 30 Remington which has broken something in the breech bolt/firing mechanism. It now has a RELEASE TRIGGER. If you pump it with the trigger held back, it will FIRE when you release the trigger. Make sure your potential buy does not do this! I don't know what it was that broke, but the assembly itself is one of the biggest whore's nightmares in the entire firearms world to assemble.
Hope this didn't scare you off . These guns were complicated, but they are also very robust and reliable. They are accurate, and as fast as any other pump rifle on follow up shots. Good luck