The Necchi BU, Nova and Supernova models have a very good reputation. These are all metal geared and will last you a life time. As to how easy they are to fixup yourself is debateable, but they should in general be up and running after a lot of oiling and cleaning (or less if the machine is rather clean). I always expect these old machines to come straight out of long term storage, very dirty and in need of care, but it's not always the case. It has been the case with mine though.
Read the manual, you will get very far with the basic maintanance routine, but as mentioned you might have to go about it very thoroughly. If you like DIY projects, there are help to be found on the web, and you can sort out the more advanced adjustment usually dealt with when it's handed in for a service. I think there's a yahoo group who has the service manual and lots of knowlegeable people there. These are models well worth investing time and money in, including handing it in to a repair shop for a full service.
For the worth, they don't sell for large amounts of money. If it's in a cabinet, in used but good condition, complete with accessories they fetch a bit more. From a different perspecitive, these were once top of the range models; a lot of time and effort were invested to make them work and last a lifetime. You would have to pay much more than the price of a good vintage machine pluss a service to get anything close to the quality of these. They don't even make this quality anymore, the exception are some industrial models. Some where on the web there is a copy of a comprehensive British consumertest made in the very early 60s. I remember two models could not be faulted after all kinds of stitch and stress tests, and it was a Necchi Supernova and a Singer 201.
Prices on used machines vary a lot, it's hard to estimate. You will be lucky to find a complete machine in nice condition and with newly made stitch samples for less than $100, but bargains turn up. I payed around $80 for a Singer 201 in a small table, and it's a straight stitch model. It needed a bit of care to run again. The last two years I have seen these Necchi models go for $70 to $180, and they were sold within a week or two. A very nice one in a cabinet caught my interest but I decided it was too far from me.
Last edited by Mickey2; 05-30-2017 at 03:09 AM.