I do have a question, any tips on how to reprogram an old Meade Autostar when you have no idea what it wants you to point it at and the little plastic viewfinder is cracked off? LOL - I should probably fix that first.
Meade, however, has parts all over the internets. This is another case where I say, go to the local club and ask them if they have spares, if they have parts they can give you or if all else fails, give you the exact parts you need to get to fix your issue. Some of the older Meade Autostars are fantastic telescopes with high end glass and mirrors. Some are also junk. Eyes on the unit are needed for more information.
Another question (should not have clicked that link!) what's the difference between the 100mm and the 127mm Mak-Cassegrain scopes, just curious as I might, uh, give that Meade to someone and get me a shiny new something, and if the 127mm is a big difference for the extra $80 then it's worthwhile to do that. What's the benefit of the EQ3 mount over the twilight nano, as I see the 127mm comes with that option for an extra $50.
Excellent questions. First on the mount, you are looking at the difference between an 'equatorial' and an 'alt-az' style mount. The equitorial is designed to be set up so that once you have an object in the telescope, you only have to move the mount in one direction to keep the object centered. Equatorial mounts take time and effort to set up, verify they are set up correctly, and are harder (IMO) to aim. An 'Alt-Az" mount moves in two directions- altitude and azimuth hence the name- to follow an object. Most Alt-Az telescopes only need to be set on the ground, leveled and boom you are going. I strongly urge beginners to get Alt-Az mounts as they are much easier to use.
Next, the telescope. The difference between the 100 and the 127 is that the 127 will collect more light- almost double the amount of light. One thing to remember about a telescope is that the scope is designed to make faint objects brighter (speaking visual use here... photography is all different). the more light you collect the brighter stuff will be at the eyepiece. Also, the bigger the telescope, the heavier it is, the bigger mount you need etc. They do not list the weight of the 127mm, but my guess is that it is at the max weight limit of the nano mount. I have a 90mm refractor on that mount, a buddy has the 100mm Mak that I linked to and we have a few people with the 114mm Newtonian. the 114mm telescope is pushing the weight limits, but still workable. I just don't like the short Newtonians like that one as they are a pain to keep adjusted.
If you have the want, and are able to save up, the absolute best deal going now for a 'beginner' telescope is an 8" Dobsonian Reflector which you can have a fully functional setup for just about $500. These telescopes are fantastic, can see all kinds of objects even in light pollution, and will last decades if you take care of them. I post this as a counter to the 127mm you were looking at. Just like computers, there is always something within $50-$100 bux that will make the system so much better so you have to decide what you want and what you are willing to compromise. I tell people to pick a price point and stop there. since you are not buying, yet, go to the local club and get your telescopes fixed. Then decide how deep you want to go into the hobby.