I have an amp that i've been playing for a few years just like this one....

and now it wont work. the power turns on but when i plug a guitar into it theres no sound. I opened it up and everything looked fine so i'm guessing the tubes just need replaced?

if thats the case then how much will this cost? is there just 1 specific tube that just needs replaced or would it possibly be multiple ones or all of them?

this was my dads amp so I don't know much about the inside of it or how it works. He's had it for awhile so its got a good amount of years on it.

also when you lift it up you can hear something rattling inside of it (the sound is similar to like a broken lightbulb or something). my dad says its been doing that for years but it still worked.

so yeeeeah please gimme some advice
well the rattling could well be the reverb tank.
and also, you should replace all of the tubes to be on the safe side, especially if they're pretty old
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I would bring it to a music store and ask them to take a look at it. Maybe there's a problem with the guitar, or even your cable.

Tube costs vary depending on the tube that you need. I presume since it's a Marshall it'll need an EL34 but again, take it to a music store.