Greetings micali, welcome to the Forum !!
That sure sounds like a solenoid problem to me, as long as you got plenty of Fluid in it, right?
My first recommendation (coming from a Standard Shift guy

) would be to run some Cleaner in it. Could save you some major cost, and would only require a Fluid and Filter Change later, IF that worked for you.
On the Speedometer problem, I think that model had a Cable, and I get under it, pull the Housting out of the Tailshaft on the Tranny, and check the Gear on it. That may be worn, and it's not a difficult fix, with a used or new gear.
Good luck, and keep us updated on it !
Have a good Day !
S.W.