Hi I just bought this sg http://imgur.com/hq5wM69. It is sanded down right to the bare mahogany and im not quite sure how to go about protecting the wood and finishing it. THe tech at the store (someone i somewhat trust) suggested lemon oil on the body but with further reading i have found that it might not be the right oil. should I use tung oil ? tru oil etc ? if in the future i wanted to restore it to its original finsih (either cherry stain or black gloss paint not really sure ) would oiling it prevent me from doing this ? also any help on the process of oiling it would be appreciated as well
Tru Oil would definitely work, but it soaks into the wood and would stop it taking a stain. You'd have to sand through as deep as the oil has soaked in, which would be a lot in mahogany.

The process of oiling depends on the finish you want. If you want high gloss, you need to fill the pores completely with either the filler/sealer or sanding with Tru Oil. After that, you just wipe thin coats on until the finish has built up. Lightly buff with #0000 steel wool every few coats to keep it level.
i dont really need a gloss finish i just want to protect the wood and leave the option of staining it open in the future , would lacquer be an option ?
Something like 2K clear is an option if you use respiratory protection and work carefully. Tru Oil is definitely the easiest, then 2K is harder to get right.
some people have said to just lemon oil it and if i do want refinish it just let the lemon oil dry out
the reason i am going with lemon oil is because in its own way its reversable and if i want to do it in a cherry stain later I still can. Am I right in think i just apply the lemon oil with a rag to the body , let it sit for 15 minutes then wipe away excess and repeat until the desired look is there ?