Faced a similar situation, although I had partial insurance. Got a root canal and a cap. Buy some better insurance and wait until it kicks in before getting the work done.
Shop around, maybe you might be able to get a better price.
The longer you wait the more likely it is all the nerves there will be dead. Not necessarily a bad thing. I had a nightmarish experience with a lower root canal.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13