Green Card extension will expire soon, how to travel

[kokesismanim]

Its been 1.5 year since USCIS received my RFE documents and I still havent got the 10 years GC. Is that normal? My GC extension will expire mid of February and I plan to go to Europe in April for 4-5 months. How is the procedure to get a travel document and how long does it take to receive? When should I apply for it if I wanna go in April and for how long is the travel document valid?

Appreciate your advices! Thank you!

[newacct]

Call USCIS to make an appointment at your local USCIS office to get an I-551 stamp on your passport. The I-551 stamp is valid for 1 year.